86,786 research outputs found
Dissecting the Extracellular Complexity of Neuromuscular Junction Organizers
No full textSynapse formation is a very elaborate process dependent upon accurate coordination of pre and post-synaptic specialization, requiring multiple steps and a variety of receptors and signaling molecules. Due to its relative structural simplicity and the ease in manipulation and observation, the neuromuscular synapse or neuromuscular junction (NMJ)—the connection between motor neurons and skeletal muscle—represents the archetype junction system for studying synapse formation and conservation. This junction is essential for survival, as it controls our ability to move and breath. NMJ formation requires coordinated interactions between motor neurons and muscle fibers, which ultimately result in the formation of a highly specialized post-synaptic architecture and a highly differentiated nerve terminal. Furthermore, to ensure a fast and reliable synaptic transmission following neurotransmitter release, ligand-gated channels (acetylcholine receptors, AChRs) are clustered on the post-synaptic muscle cell at high concentrations in sites opposite the presynaptic active zone, supporting a direct role for nerves in the organization of the post-synaptic membrane architecture. This organized clustering process, essential for NMJ formation and for life, relies on key signaling molecules and receptors and is regulated by soluble extracellular molecules localized within the synaptic cleft. Notably, several mutations as well as auto-antibodies against components of these signaling complexes have been related to neuromuscular disorders. The recent years have witnessed strong progress in the understanding of molecular identities, architectures, and functions of NMJ macromolecules. Among these, prominent roles have been proposed for neural variants of the proteoglycan agrin, its receptor at NMJs composed of the lipoprotein receptor-related protein 4 (LRP4) and the muscle-specific kinase (MuSK), as well as the regulatory soluble synapse-specific protease Neurotrypsin. In this review we summarize the current state of the art regarding molecular structures and (agrin-dependent) canonical, as well as (agrin-independent) non-canonical, MuSK signaling mechanisms that underscore the formation of neuromuscular junctions, with the aim of providing a broad perspective to further stimulate molecular, cellular and tissue biology investigations on this fundamental intercellular contact
Phasing protein structures using the group–subgroup relation
No full textDiffraction data from two non-isomorphous crystals (forms 1 and 2) of an artificial protein with a four-helix bundle motif, di-CoII-DF1-L13A, have been collected using synchrotron radiation. The phase of form 1 has been assigned using the group and minimal non-isomorphic supergroup relation between the space group of the previously determined di-MnII-DF1-L13G structure and the space group of this form. This unconventional method of solving the phase problem has also been tested with form 2 using a reverse relation. The structure of the latter form has been solved using the group and maximal non-isomorphic subgroup relation with the space group of form 2 of the analogous dimanganese protein. This application has shown that this phasing method can be used for solving the protein structures of polymorphic crystals as an alternative to the molecular-replacement method
Expression of adrenomedullin and its receptors in the human adrenal cortex and aldosteronomas
No full textAdrenomedullin (ADM) is a hypotensive peptide, that derives from the proteolytic cleavage of pro(p)ADM and acts through at least two subtypes of receptors, called L1-receptor (L1-R) and calcitonin receptor-like receptor (CRLR). CRLR may function as a calcitonin gene-related peptide (CGRP) or a selective ADM receptor depending on the expression of the subtype 1 or the subtypes 2 and 3 of a family of proteins, referred to as receptor-activity-modifying proteins (RAMPs). Although adrenal cortex is known to be one of the main target organs of ADM, its expression of the ADM and its receptor has not yet been extensively investigated. Reverse transcription (RT)-polymerase chain reaction (PCR) revealed the expression of the pADM and peptidyl-glycine alpha-amidating monooxigenase (PAM) genes in four human adrenal cortexes and four aldosteronomas. Since PAM is the enzyme that converts immature ADM to the mature and active form, these findings suggest that the two tissues are able to produce ADM. RT-PCR also demonstrated high levels of L1-R mRNA and relatively low levels of CRLR mRNA, as well as the presence of specific mRNAs for the three RAMPs, thereby indicating that human adrenal cortex and aldosteronomas are provided with the two subtypes of classic ADM receptors. In conclusion, our investigation provides the first evidence that human adrenal cortex and aldosteronomas express the ADM system, that may play a role in the paracrine or autocrine control of their functions
Il recupero di aree marginali con il pascolamento: approccio metodologico alla carta della vegetazione in scala 1:5.000 del Monte Pavaglione (Appennino ligure)
No full textExploring Decision Transformer for Highway Automated Driving
No full textThe evolution of Automated Driving Functions (ADFs) is contingent upon the effective implementation of Decision-Making (DM), context perception, and predictive vehicle control. Conventional Deep Reinforcement Learning (DRL) methodologies frequently prove inadequate in dynamic settings, largely due to their inherent limitations in addressing real-time DM and assigning long-term credit. DRL via sequence modeling represents a promising avenue for addressing these challenges by combining the strengths of Attention-based architectures, such Transformer, and DRL. The integration of self-attention mechanisms with offline DRL enables long-term credit assignment, fine-tuning and prevent continuous interaction with the environment, mitigating risks related to real-world simulations and trial-and-error approaches. This paper examines the potential of Decision Transformer (DT) within the AD domain. A DT model was implemented and trained within the highway-env simulation environment. To do so, an offline RL dataset was constructed using a pre-trained Deep Q-Network (DQN) agent. The model was evaluated by comparing its performance against that of the pre-trained DQN and a random agent. Results demonstrated that the DT model exhibited superior DM capabilities, with higher average returns and longer episode durations than DQN. These findings highlight the potential of Transformer-based DRL in AD
New roles of flavoproteins in molecular cell biology: histone demethylase LSD1 and chromatin
No full textLysine-specific demethylase 1 (LSD1) is an enzyme that removes methyl groups from mono- and dimethylated Lys4 of histone H3, a post-translational modification associated with gene activation. Human LSD1 was the first histone demethylase to be discovered and this enzymatic activity is conserved among eukaryotes. LSD1 has been identified in a number of chromatin-remodeling complexes that control gene transcription and its demethylase activity has also been linked to pathological processes including tumorigenesis. The 852-residue sequence of LSD1 comprises an amine oxidase domain which identifies a family of enzymes that catalyze the FAD-dependent oxidation of amine substrates ranging from amino acids to aromatic neurotransmitters. Among these proteins, LSD1 is peculiar in that it acts on a protein substrate in the nuclear environment of chromatin-remodeling complexes. This functional divergence occurred during evolution from the eubacteria to eukaryotes by acquisition of additional domains such as the SWIRM domain. The N-terminal part of LSD1, predicted to be disordered, contains linear motifs that might represent functional sites responsible for the association of this enzyme with a variety of transcriptional protein complexes. LSD1 shares structural features with other flavin amine oxidases, including the overall fold of the amine oxidase domain region and details in the active site that are relevant for amine substrate oxidation
LSD1 : oxidative chemistry for multifaceted functions in chromatin regulation
No full textThree years after its discovery, lysine-specific demethylase 1 remains at the forefront of chromatin research. Its demethylase activity on Lys4 of histone H3 supports its role in gene repression. By contrast, the biochemical mechanisms underlying lysine-specific demethylase 1 involvement in transcriptional activation are not firmly established. Structural studies highlight a specific binding site for the histone H3 N-terminal tail and a catalytic machinery that is closely related to that of other flavin-dependent amine oxidases. These insights are crucial for the development of demethylation inhibitors. Furthermore, the exploration of putative non-histone substrates and potential signaling roles of hydrogen peroxide produced by the demethylation reaction could lead to new paradigms in chromatin biology
Crystal structure of the kringle domain of human receptor tyrosine kinase-like orphan receptor 1 (hROR1)
No full textReceptor tyrosine kinase-like orphan receptors (RORs) are monotopic membrane proteins belonging to the receptor tyrosine kinase (RTK) family. RTKs play a role in the control of most basic cellular processes, including cell proliferation, differentiation, migration and metabolism. New emerging roles for RORs in cancer progression have recently been proposed: RORs have been shown to be overexpressed in various malignancies but not in normal tissues, and moreover an abnormal expression level of RORs on the cellular surface is correlated with high levels of cytotoxicity in primary cancer cells. Monoclonal antibodies against the extracellular part of RTKs might be of importance to prevent tumor cell growth: targeting extracellular kringle domain molecules induces the internalization of RORs and decreases cell toxicity. Here, the recombinant production and crystallization of the isolated KRD of ROR1 and its high-resolution X-ray crystal structure in a P3121 crystal form at 1.4 Å resolution are reported. The crystal structure is compared with previously solved three-dimensional structures of kringle domains of human ROR1 and ROR2, their complexes with antibody fragments and structures of other kringle domains from homologous proteins
The application of Lake Shorezone Functionality Index (SFI): a valid tool to assess the reproductive sites status of bleak (Alburnus arborella)
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