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Growing Agricultural Literacy: Investigating Knowledge and Attitudes Toward Climate-Smart Agriculture and Food Security
No full textIn an era of increasing global populations, agricultural literacy emerges as a critical need for sustainable engagement with the Earth's resources. This study seeks a comprehensive exploration of agricultural literacy, aiming to understand its complex scope, assess existing gaps, and propose strategies for improvement. As societies expand, both direct stakeholders in agriculture and consumers reliant on its products necessitate a comprehension of farming practices, challenges, and innovations to navigate a sustainable path forward.
Agricultural literacy is part of daily life yet, despite agriculture's presence in daily life, a visible gap exists in public understanding. Furthermore, perceptions toward agriculture, particularly regarding climate-smart practices, emphasize the need for directed initiatives to bridge knowledge divides and dispel misconceptions.
By understanding the relationship between agricultural literacy and attitudes toward climate-smart agriculture, this study aims to explain pathways for strengthening comprehension and advancing sustainable practices. Knowledge gaps and misconceptions pave the way for tailored educational programs and policy frameworks aimed at nurturing agricultural literacy. A descriptive and correlational design was used for this study to describe the participants and relationships among factors being education, age, attitudes toward food and agriculture, and climate-smart agriculture. A questionnaire was sent to participants electronically which took approximately 10 minutes. Results were analyzed using statistical analysis ANOVA, mean, standard deviation, percentages, regressions, and frequencies.
Furthermore, the impacts of these efforts extend to education systems, envisioning a complete incorporation of agricultural literacy into all levels of education. From primary school curricula to college education, embedding agricultural literacy not only imparts essential insights into food systems and environmental stewardship but also instills a profound appreciation for global interdependencies. By nurturing a sense of agency and stewardship, agricultural literacy education propels future toward roles as consumers, innovative agrarians, and champions of climate-smart agriculture.
Understanding agriculture becomes not just desirable but necessary to feed growing populations. By working together across disciplines—among policymakers, educators, researchers, and communities—we can move towards a future where knowing about agriculture is fundamental for making informed decisions and caring for our resources. Together, we aim for a sustainable food system that meets current needs and fulfills future goals
Optimal control strategies of lithium-ion battery based on electrochemical thermal life model for hybrid electric vehicle and fast charging applications
No full textLithium-ion batteries (LiBs) are the most crucial component of electric vehicles (EVs) and hybrid electric vehicles (HEVs) with respect to cost and performance. Development of optimal control strategies for EVs and HEVs is essential for safe and durable battery use. For analysis and controller design purposes, reduced-order electrochemical-thermal-life models (ROM) are developed, validated, and optimized considering accuracy and computational time. By utilizing the model, optimal energy management strategies (EMSs) are developed for HEVs, and optimal Fast Charging (FC) protocols are developed for EVs.
HEVs have complex configurations using multiple power sources, including engines and single or multiple motors. EMS is a control strategy that decides the power split between the power sources. However, battery degradation has not been considered, which is necessary for durable battery usage. Therefore, a new EMS is developed that improves fuel efficiency (FE) and suppresses the degradation of the battery. A hybridized two layer algorithm that combines multi-objective nonlinear model predictive control (NMPC) with a rule-based (RB) algorithm is proposed as a new EMS that is called RB-NMPC. The RB-NMPC is designed to optimize the torque split between the engine and electric motors while maintaining the maximum and minimum constraints of each component. The proposed EMS is incorporated into control-oriented vehicle models, and their performances are analyzed for different driving cycles by comparing with RB, dynamic programming (DP), and NMPC.
The long charging time of EVs is a remaining issue for their further commercialization. Based on the validated ROM, two new FC protocols have been developed considering thermal and aging effects. Firstly, we propose an optimized MCC (O-MCC) charging protocol suppressing Lithium Plating (LiP) based on the battery’s State of Health (SOH). Secondly, we propose an optimized MCC protocol with negative pulses (O-MCC+NP) to simultaneously suppress LiP formation and recover lithium-ions via lithium stripping (LiS). The current amplitudes are optimized using NMPC algorithms under constrained LiP. Pulse frequency is determined experimentally, reducing heat generation associated with diffusion resistance by Distribution of Relaxation Time (DRT) analysis. The proposed two new charging protocols are experimentally tested and compared with commercial charging protocols.
Lastly, accurate and real-time estimation of SOH is also important for the safe and durable use of HEVs and EVs. Machine Learning (ML) based data-driven approaches gaining popularity in industries, offering a promising alternative to model-based state estimation methods without any knowledge of electrochemical principles. However, their accuracy for FC conditions has not been verified by using only real-time obtainable data. Therefore, we propose an optimized Neural Network (NN) model that achieves accurate SOH predictions across various temperature ranges and charging profiles, which is essential for real-time applications in HEVs and EVs. Moreover, the ML-based SOH estimation algorithm is incorporated with the O-MCC protocol, verifying the performance in Battery-in-the-loop (BIL) system.
The model improvement considering mechanical degradation and verifying the control algorithms for batteries with different chemistries are considered as future works
Chronic Wasting Disease in the United States: How Have Hunters and State Wildlife Agencies Responded?
Get PDFChronic wasting disease (CWD), a fatal neurodegenerative disease that affects cervids, has been detected in 33 states across the United States. Currently there are no preventions, treatments, or cures for the disease in cervid populations, which makes the disease a significant looming threat for managers to address. Wildlife managers and decision-makers, due to presence and spread of CWD within states, are addressing the following challenges posed by CWD including negative impacts on cervid populations, drops in hunter participation, and related loss of revenue from hunting license sales. Impacts like the decline in hunting license sales could have serious repercussions for the way we fund conservation in the United States. Our first study sheds a greater light on some of the most pressing challenges and uncertainties facing wildlife managers, specifically examining what may cause hunters to stop hunting when CWD comes to their state. Our research studies hunter perceptions of risk, concern, and comfort associated with CWD in newly affected states. We found that hunter perceptions varied significantly, influenced by a variety of factors including demographics, hunting-specific demographics, hunting motivations, and proximity to detection. Thus, we concluded that hunter perceptions about the detection of CWD were not generalizable to a newly affected region. Additionally, we investigated the impact of state wildlife agency policies on annual CWD prevalence. States with written CWD management plans that had bans on baiting and natural cervid urine lures exhibited lower annual prevalence rates than states that permitted baiting. Conversely, states that had special CWD hunting opportunities (e.g. an additional season) and bans on rehabilitation of cervids within established CWD zones exhibited greater annual prevalence. These findings underscore the complexities of CWD management and emphasize the necessity of multifaceted approaches
Behavior of Steel Drop-In Connections Evaluated Utilizing Digital Image Correlation
Get PDFA safer and more efficient drop-in shear connection (compared to conventional shear tab
and double angle connections) has been proposed for implementation in the commercial and
residential steel frame building industry. This effort is part of the American Institute of Steel
Construction’s (AISC’s) Need for Speed Initiative to reduce the steel construction cycle by 50%.
The objective of this thesis is to aid in the development of a future design process for the
proposed connection by evaluating the behavior of its various components, specifically the
connection angles, girder top flange, and column web, through full-scale testing. Eleven various
drop-in connections were tested in realistic girder-to-column and beam-to-column test setups at
Auburn University’s Advanced Structural Engineering Laboratory. Six girder top flanges and
eight angles were observed and analyzed utilizing Digital Image Correlation (DIC), an
established optical technique that allows for the visualization of complete strain fields on a
specimen’s surface. As well, two-column webs were observed via DIC for a typical one-sided
beam-to-column connection, like that which is utilized for an exterior beam in a building.
Testing revealed various ductile failure modes, such as transverse and longitudinal
bending of the girder’s top flange, allowing for large plastic deformations to occur before
ultimate failure. It was determined, through surface strains observed on the vertical angle legs,
that the current AISC equation to determine single-angle leg shear strength would be adequate
for the design of the tested connection angles. Finally, when utilizing a one-sided beam-to
column connection in which the angles are attached to the column web, plastic deformation of
the web may occur and should be checked
Theory and Simulation of Transient Phonon Heat Conduction in Crystals
No full textFirst-principles calculations based on phonon Boltzmann transport theory have demonstrated that the phonon gas model is generally applicable for crystalline solids. However, this model is known to break down in some specific cases, such as in solids near their melting temperature or in highly conductive solids at low temperatures.
The first part of this dissertation focuses on assessing the validity of the phonon gas model at very high temperatures, particularly near the melting point. To achieve this, we implemented a computational algorithm to interpret experimental neutron or x-ray single-phonon scattering spectra using molecular dynamics-simulated single-phonon Green’s functions as input. In the case of silicon crystals, we find that the single-phonon approximation remains valid up to the melting temperature of 1600 K. However, perturbative calculations based on lower-order anharmonicity significantly underestimate the renormalized phonon frequency and phonon lifetime, underscoring the importance of non-perturbative models for renormalized phonon spectra at very high temperatures.
In the second part of this dissertation, we examine non-Fourier heat conduction phenomena under hydrodynamic conditions using a new theoretical framework for transient heat conduction. Through statistical analysis of a unified formula for transient heat flux in phonon gases, we propose a time-dependent Zwanzig theory for transient heat conduction, applicable in both the phonon second sound limit and the Fourier diffusion limit. A key finding of this work is the necessity of incorporating phonon heat dissipation dynamics into heat conduction theory via heat current Green’s functions. Our theory unveils the coexistence of both wave and diffusion dynamics across different temperatures and material types, with their interplay depending on time and length scales. We have calculated the phonon heat current Green's functions for silicon over the temperature range of 30 K to 300 K and compared our model with experimental data from transient thermal techniques, such as transient thermal grating experiments
Enhancement in NaCl aerosol filtration in a filter media through the use of porous fibers with multiscale, multidomain porosities: Unveiling novel filtration mechanisms governed by capillary and thermodynamic forces.
Get PDFStudying NaCl aerosol filtration holds significant importance for several reasons. It is commonly used as a standard challenge aerosol for testing air filter media because it resembles properties of many airborne particles. Additionally, filtration of NaCl aerosols plays a crucial role in various marine applications. In marine environment, which is abundant with NaCl aerosols, filtration of NaCl aerosols becomes imperative to protect air breathing equipment aboard high-speed marine vessels like LCACs and ships. Equipment such as gas turbines and Solid Oxide Fuel Cells rely on clean air for optimal performance. Failure to filter NaCl aerosols can lead to their deposition on these equipment, resulting in corrosion and damage, thus reducing their operational lifespan.
Traditional fibrous filters employ solid fibers such as glass fibers which has no intra-fiber porosity. They capture particulates onto the fiber surface using mechanism/s like inertial impaction, interception and diffusion.
NaCl is hygroscopic in nature and exists in either solid, hydrated or liquid states depending on Relative Humidity (RH). Porous hydrophilic fibers can be utilized to wick these hygroscopic particles into their wet (i.e. condensed) pores, potentially enhancing both the filtration performance and the loading capacity when used as filter fibers. Therefore, this study investigates novel NaCl filtration mechanisms which are uniquely available to filter media composed of nanoporous hydrophilic fibers.
The first mechanism involves the dissolution of dry, solid NaCl aerosols deposited onto the surface of Activated Carbon Fibers (ACFs) into the wet intrafiber porosity of ACFs. ACFs, which are hydrophilic fibers, have intrafiber pores condensed with water, even at low RH conditions due to a combination of physisorption, chemisorption and capillary forces. The dry NaCl particles get dissolved and wicked into the water-filled pores, facilitated by the favorable thermodynamics of NaCl dissolution in water. The second mechanism involves direct wicking and capillary condensation of aqueous NaCl into the intrafiber porosity of ACFs. The third mechanism involves the utilization of nanofibers in the form of a floc, as opposed to a continuous layer spanning the entire flow path. Vapor Grown Carbon Fiber (VGCF) nanofiber floc has a high surface-to-volume ratio, and extensive intra-floc porosity. Traditional nanofiber filter media uses nanofibers as a surface layer which spans the entire flow path, increasing the flow resistance. If used in filtration of NaCl aerosols, these media will clog after brief use, and go into a high pressure drop state. The VGCF nanofiber flocs do not span the flow path, thus providing negligible flow resistance. The nanofiber flocs capture NaCl aerosols at low RH conditions via slip-flow, increasing filtration efficiency without anticipated increase in pressure drop. The flocs absorb wet NaCl aerosols in a sponge-like fashion.
To elucidate these novel filtration mechanisms, a novel fibrous depth filter media comprising multi-scale, multi-domain porosity was designed by embedding VGCF nanofiber flocs into a matrix of ACFs, held together by a binder fiber. This media consists of three distinct porosity domains: 1) Intrafiber porosity of ACF (0.950 cm3/gm), 2) Intra-floc porosity of VGCF flocs (4.108 cm3/gm), and 3) Interfiber porosity among all fibers (11.7 cm3/gm). For comparative analysis, ACF filter media was synthesized without VGCF flocs to examine the impact of their absence on NaCl aerosol filtration. Similarly, filter media made of non-porous Graphite fibers were also included to understand the impact of the absence of intrafiber porosity on NaCl aerosol filtration.
This thesis comprises three different studies to understand the filtration of NaCl aerosols. The first study involves NaCl filtration using ACF filter media and Graphite filter media. Filtration performance metrics including pressure drop, filtration efficiency, Quality Factor, and NaCl loading capacity were evaluated to understand the effect of intrafiber porosity on NaCl aerosol filtration. SEM and EDS analyses were performed to verify the movement of NaCl into the intrafiber pores of ACFs. The second study focuses on NaCl aerosol filtration using ACF media with and without VGCF flocs. Same filtration performance metrics were evaluated to assess the impact of nanofiber flocs on NaCl aerosol filtration. SEM and EDS analyses were also conducted to verify the transport of NaCl into the intrafloc porosity of VGCF flocs. Third study analyzes the deliquescence of NaCl aerosols and their interaction with ACFs, VGCF flocs and Graphite fibers. SEM and EDS (including Cl mapping) were performed to understand the interaction of aqueous NaCl with the three aforementioned filter fibers.
The Quality Factor of ACF media with VGCF flocs was higher than Graphite media when filtering both low and high RH NaCl aerosols. This is due to slip-flow occurring at nanofiber surfaces of VGCF flocs enabling capture of NaCl aerosols without anticipated pressure drop. Due to wicking of NaCl in ACF nanopores combined with NaCl entrapment into highly porous VGCF flocs, the NaCl loading capacity of ACF media was 1200% (or 12X) higher than that of media made with non-porous Graphite fibers, on loading low RH NaCl aerosols. This capacity increased by another 315% (or 3.15X) when filtering high RH NaCl aerosols, due to ease of wicking liquid aerosol droplets into both ACF pores and VGCF flocs. The transport of NaCl inside the intrafiber nanopores of ACFs, as well as within the intra-floc porosity of VGCFs was confirmed by EDS analysis.
The inclusion of VGCF nanofiber flocs into ACF media increased both the filtration efficiency and Quality Factor by a two-fold increase, compared to ACF media without VGCF flocs. This was observed at both low and high RH conditions. This is attributed to wall-slip at nanofiber surfaces of VGCF flocs, enabling efficient capture of NaCl aerosols without anticipated increase in pressure drop. Without VGCF flocs, the ACF media showed unacceptable performance (FE and QF). Furthermore, at high RH, ACF media without VGCF flocs never reached a breakthrough point. The NaCl loading in ACF media with VGCF flocs increased by 315% on going from low RH condition to high RH condition. This enhancement at high RH is primarily due to wicking of aqueous NaCl directly into the extensive pore volume of VGCF flocs in a sponge-like manner, and secondarily due to wicking of aqueous NaCl directly into the intrafiber nanopores of ACFs. EDS analysis showed higher Cl:C ratio in the flocs compared to ACFs, particularly under high RH conditions, confirming the importance of VGCF flocs in ACF media for NaCl aerosol filtration. More importantly, preferential loading of VGCF flocs was observed with chlorine mapping, further emphasizing the importance of VGCF flocs in NaCl aerosol filtration.
This study also confirmed the deliquescence of NaCl particles on different filters and investigated the interaction of the deliquesced NaCl with various filter fibers including ACFs, VGCF flocs and Graphite fibers. Deliquescence of NaCl was observed in all these fibers on exposing humid (75% RH) air to the samples loaded with NaCl. Although optical microscopy was not able to capture the phenomenon of wicking of deliquesced NaCl into ACF pores, it was able to capture the wicking of aqueous NaCl into VGCF nanofiber flocs. The deliquesced NaCl remained on the surface of the Graphite fiber as droplets
Anomaly Resilience, Detection, and Reaction in Astrodynamics Problems
No full textThis manuscript is divided into three parts, each associated with three of the main projects I undertook throughout my doctoral journey. In particular, this dissertation focuses on the topics of anomaly resilience, detection, and reaction in astrodynamics problems, which are crucial aspects to consider for ensuring mission success, especially when dealing with the harsh space environment. In this manuscript, resilience, detection and reaction are investigated in two selected domains: trajectory design in cislunar regime and satellite constellations, both susceptible to the possibility of unexpected events. Therefore, effective identification capabilities and swift reaction to unforeseen phenomena become vital to support mission integrity.
Resilience to off-nominal behaviors is investigated for the trajectory design problem in the first part of this manuscript. In particular, we explore the convergence and dynamical structure of the trajectory design space associated with lunar landing and ascent abort scenarios for a crewed module departing from and returning to the Deep Space Gateway. Numerical methods for the identification of abort trajectory solutions are employed within a two-step optimization pipeline, through which we discover the existence of regions of stiff convergence where traditional pipelines may fail. Hence, we present an extensive analysis of problem parameters, demonstrating how the presence of such regions can be traced to the formulation of employed correction algorithms, problem dynamics sensitivity, and transfers geometry. To reduce the computational cost, we introduce a three-step optimization pipeline relying on surrogate models trained via adaptive sampling for the fast generation of initial guesses, which are then corrected for the recovery of abort trajectories within the defined scenario. Results obtained from the application of the optimization pipeline on the two scenarios underscore the complexity of the solution space, while providing useful information to inform the trajectory design process.
Anomaly detection and reaction in the context of Proliferated Low Earth Orbit (P-LEO) satellite constellations are then explored in the remaining two parts of this manuscript, with a focus on anomalous behaviors originating from adversarial actions against a constellation. For the detection problem, we present a transformer neural network- based pipeline for the identification of anomalous connections between satellites, modeling a P-LEO as a dynamic graph, which is capable of capturing spatial-temporal correlations characterizing a temporal network. Our analyses demonstrate how temporal and spatial signals alone are insufficient for effectively discriminating anomalous connections, requiring additional features to enrich the information extracted from the network dynamics. Notably, we discover how the introduction of edge-frequency information positively impacts our algorithm performance, reaching up to 95% in AUC score, here used as quality metric. Additionally, extensive analyses on variations of problem parameters demonstrate the robustness of the method over a wide range of scenarios, and highlight the existence of interesting couplings between satellite dynamics, spatial ground node distribution, and algorithm performance.
For the reaction component, a combination of competitive coevolutionary algorithms and genetic programming is employed to evolve reactive strategies to respond to adversarial actions against a constellation system. In particular, genetic programming trees are employed for the representation of reactive policies to respond to presented and different, unseen scenarios. The analysis demonstrates how the utilized approach provides effective solutions, beating both minimally complex strategies and human-developed ones, and showing adaptability to the introduction of multiple constraints. In both the detection and reaction problems, the proposed methodologies display the potential to reduce the cognitive load on operators of large constellation systems, and to possibly enable resolution of critical situations in a timely manner
Gene editing for growth enhancement in channel catfish, Ictalurus punctatus, and xenogenesis in common carp, Cyprinus carpio to produce blue catfish, I. furcatus, sperm
Get PDFXenogenesis is a method of reproduction where successive generations differ from each other and no genetic material is transmitted from the parent to the offspring. Xenogenesis can be accomplished by transplanting spermatogonial stem cells (SSCs), oogonial stem cells (OSCs) or primordial germ cells (PGCs) from the desired diploid donor species into a sterilized host. Many beneficial ecological and aquaculture applications are possible from this process. Specifically, the production of embryos from hybridizing channel catfish (Ictalurus punctatus) females with blue catfish (I. furcatus) males could be refined to a simpler and more cost-effective practice of xenogenesis. Xenogenesis could alleviate the reliance on growing blue catfish males to maturity and sacrificing them for gonad extraction and subsequent artificial spawning. Male blue catfish cannot be stripped of milt for artificial fertilization and must be sacrificed for sperm collection. Thus, one objective was to produce xenogenic common carp, Cyprinus carpio, to become biological blue catfish milt factories.
Common carp embryos, and larvae were injected with blue catfish oogonial stem cells and spermatagonial stem cells at various points in relation to their development. Fish were injected beginning at 0-degree days, every 23-degree days until 621-degree days. In total, 152 potential common carp xenogens were sampled and 57 of them were confirmed to be hosting blue catfish stem cells through polymerase chain reaction (PCR), giving a total 37.5% success rate of common carp hosting blue catfish cells in the gonads. The highest percentage of positive samples were observed at 0 to 46-degree days and 483-575 degree days, averaging 62.3% and 56.7% success respectively. Rate of xenogenesis was similar for male and female common carp hosts. The mean survival among all the treated groups through the first 34 days was 47%, however, among groups injected during embryonic development, mean survival was 8.6%. During the grow out stage (34-545 dpf), mean survival for all treated groups was 70%. At one and half years of age, xenogenic common carp males produced blue catfish sperm based upon DNA analysis of the expressed sperm.
In addition to stronger reproductive control, some targeted genetic alterations were performed to aid in higher growth rates and increase yield within catfish aquaculture. Two induced mutations were investigated, melanocortin-4 receptor (mc4r) and myostatin (mstn) gene in channel catfish. In a earthen pond environment stocked at 18,508 fish per hectare, the mean weight for channel catfish mc4r P1, mc4r F1 X control, control X mc4r F1, and mc4r F1 X mc4r F1 mutants was 361, 266, 521, and 426 grams, respectively, was larger (P>0.05,P>0.05, P<0.01, P<0.01) than control (C) channel catfish, 299 grams. In a recirculating system environment, during the first year of growth (354 days post fertilization), channel catfish mc4r F1 mutants had a mean weight of 22.6 grams and channel catfish controls were 10.5 grams, a 73.3% increase in body weight in the mutant fish (P<0.0001). During the next 161 days, mc4r mutants grew 29.2% faster (P<0.0001) than controls, reaching mean body weights of 66.6 grams and 49.7 grams respectively. Additionally, the effects of a CRISPR/Cas9 mediated mc4r and myostatin (mstn) gene knockouts on disease resistance to Flavobacterium covae, in channel catfish and blue catfish (I.furcatus) were examined. Both mc4r and mstn channel catfish mutants had better survival (P=0.0061, P=0.0150) when challenged with F. covae compared to the control channel catfish. Observed survival of blue catfish mc4r mutants was higher than blue catfish controls but was not significantly different (P=0.21)
Exploring the Impact of Obesity, Type 2 Diabetes Mellitus, Nerve Growth Factor, and Exercise on Skeletal Muscle
No full textSkeletal muscle is the largest organ of the body with many essential functions. Recent studies have linked obesity and type 2 diabetes mellitus (T2DM) with skeletal muscle loss and dysfunction. The first objective of this study was to investigate the effects of obesity, T2DM, and nerve growth factor (NGF) on skeletal muscle atrophy markers. Examination of several molecular pathways associated with muscle atrophy revealed increased levels of atrophy markers in obese and T2DM model. Moreover, NGF was shown to mitigate these levels through inhibition of myostatin cleavage and subsequent translocation of FoxO1 transcription factor. Obesity has been shown to affect skeletal muscle fiber type proportions, reducing overall oxidative capacity, which fuels the development of insulin resistance in skeletal muscle. Thus, the second part of the dissertation work aimed to investigate mitochondrial markers in the skeletal muscle of obese and T2DM mouse model. Although there was no significant difference in the mitochondrial markers of both obese and T2DM model, NGF treatment was shown to elevate the markers associated with mitochondrial biogenesis and fusion, highlighting potential effects of NGF in alleviating dysfunctional mitochondria often associated with metabolic diseases. Moderate-intensity exercise has been recognized to increase the content and quality of mitochondria in skeletal muscle. This third part of the dissertation work revealed reduced mitochondrial markers in the muscle of obese mouse model, which were effectively elevated in the exercised obese counterparts. The increase in mitochondrial markers was shown to be associated with enhanced mitochondrial biogenesis and fission
Regulation of human melanocortin-5 receptor by melanocortin-2 receptor accessary proteins and functional characterization of hMC5R mutants
No full textMelanocortin-5 receptor (MC5R) is the most recently discovered melanocortin receptor (MCR). It is widely distributed in both central nervous system and peripheral tissues and has unique tissue expression patterns, pharmacological properties, and physiological functions. MC5R influences exocrine gland function and regulates energy metabolism by affecting lipolysis, fatty acid oxidation, and glucose uptake in adipocytes. Preliminary clinical studies also indicated that hMC5R is associated with obesity and type 2 diabetes.
Melanocortin-2 receptor accessory proteins (MRAPs) are important regulators of MCRs, which can regulate their transport, binding, and signal transduction, thereby affecting various physiological processes. There are two members of MRAP family: MRAP1 and MRAP2. Many studies have shown that MRAP1 and MRAP2 primarily interact with MC2R, MC3R, and MC4R. However, the interaction between different isoforms of MRAPs and MC5R is still unclear and needs further study.
To investigate the effects of MRAPs on trafficking, ligand binding and signaling properties of human (h) MC5R, HEK293T cells were transiently co-transfected with plasmids encoding MC5R and different isoforms of MRAPs (hMRAP1a, hMRAP1b, hMRAP2a, hMRAP2b, and hMRAP2c). The results showed that hMRAP1a, hMRAP2a and hMRAP2c increased the cell surface expression of hMC5R. All MRAPs have no effect on affinity to the superpotent analog of a-melanocyte stimulating hormone (a-MSH), NDP-MSH, while hMRAP2c significantly increased maximal binding. All MRAPs had no effect on a-MSH-stimulated cAMP production (Gas-cAMP pathway). Additionally, a-MSH induced ERK1/2 activation of hMC5R. Cells co-transfected with hMC5R and hMRAP1a, hMRAP2a, hMRAP2b, or hMRAP2c had significantly increased pERK1/2 level upon stimulation with a-MSH. In summary, the two MRAP1s and three MRAP2s had differential effects on MC5R trafficking, binding, and signaling. These findings led to a better understanding of the regulation of MC5R by MRAP1s and MRAP2s.
Melanocortin-4 and -5 receptors (MC4R and MC5R) play important roles in regulating energy homeostasis. MRAP2 regulates MC4R and MC5R trafficking, ligand binding, and signaling. Loss of MRAP2 function results in reduced MC4R activity, leading to obesity and metabolic disorders. In this study, we selected five hMRAP2a mutants (G31V, F62C, N77S, K102*, and P195L) and investigated their effects on hMC4R and hMC5R pharmacology. In hMC4R, F62C and P195L reduced cell surface expression and maximal response to a-MSH. Additionally, hMRAP2a and the remaining three mutants (G31V, N77S, and K102*) reduced the maximal response to a-MSH as well as basal activity. For hMC5R, K102* reduced total and cell surface expression. Furthermore, F62C and P195L reduced cell surface expression of hMC5R, whereas N77S increased it. F62C reduced the maximal response to a-MSH, while P195L impaired both the maximal binding and the maximal response to a-MSH. Like MC4R, MC5R exhibits basal cAMP signaling, which was reduced by hMRAP2a and all five mutants. In conclusion, hMRAP2a and its identified obesity-associated mutants can modulate the pharmacology of hMC4R and hMC5R. Different hMRAP2a mutants exhibited distinct regulatory effects on hMC4R and hMC5R, revealing a complex regulatory mechanism within the melanocortin receptor family.
Recent genomics studies have identified hundreds of naturally occurring MC5R mutations. Human MC5R is primally coupled to Gas, resulting in increased intracellular cAMP. Studies have shown that some missense polymorphisms in hMC5R affect its ligand binding activity and downstream functions, particularly those involving conserved amino acids in the transmembrane domain (TMD). Herein, we studied pharmacological properties of 12 hMC5R mutants at highly conserved residues by measuring their expression, ligand binding and signaling. Results showed only Y295H had decreased total expression while I294T had increased cell surface expression. D119Y, P253L, P292S, I294T, and I294M were defective in ligand binding as well as a-MSH-stimulated cAMP production. The remaining seven mutants (P70A, Y141F, R158H, R158L, D291H, Y295C, Y295H) had similar binding affinities for a-MSH as wild-type hMC5R. P70A, Y141F, and R158H had significantly decreased maximal binding and signaling. D291H, Y295H and Y295C were defective in a-MSH-stimulated Gas-cAMP signaling pathway. Y141F and R158H also had decreased a-MSH potency. In summary, we did not identify any mutant with misfolding defect. Five mutants had defects in binding and consequent signaling. Three mutants had binding but no signaling, with a clear defect in G protein binding and/or activation