Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0036341 (schizophrenia)
 60,220 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuronal glycoprotein M6a is involved in neuronal plasticity, promoting neurite and filopodia outgrowth and, likely, synaptogenesis. Polymorphisms in the human M6a gene GPM6A have recently been associated with mental illnesses such as schizophrenia, bipolar disorders, and claustrophobia. Nevertheless, the molecular bases underlying these observations remain unknown. We have previously documented that, to induce filopodia formation, M6a depends on the association of membrane lipid microdomains and the activation of Src and mitogen-activated protein kinase kinases. Here, in silico analysis of the phosphorylation of tyrosine 251 (Y251) at the C-terminus of M6a showed that it could be a target of Src kinases. We examined whether phosphorylation of M6a at Y251 affects neurite and filopodia outgrowth and the targets involved in its signal propagation. This work provides evidence that the Src kinase family and the phosphatidylinositide 3-kinase (PI3K), but not Ras, participate in M6a signal cascade leading to neurite/filopodia outgrowth in hippocampal neurons and murine neuroblastoma N2a cells. Phosphorylation of M6a at Y251 is essential only for neurite outgrowth by the PI3K/AKT-mediated pathway and, moreover, rescues the inhibition caused by selective Src inhibitor and external M6a monoclonal antibody treatment. Thus, we suggest that phosphorylation of M6a at Y251 is critical for a specific stage of neuronal development and triggers redundant signaling pathways leading to neurite extension.
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PMID:Tyrosine 251 at the C-terminus of neuronal glycoprotein M6a is critical for neurite outgrowth. 2524 28

Neuronal glycoprotein M6a belongs to the tetraspan proteolipid protein (PLP) family. Mutations in GPM6A gene have been related to mental disorders like schizophrenia, bipolar disorders and claustrophobia. M6a is expressed mainly in neuronal cells of the central nervous system and it has been extensively related to neuronal plasticity. M6a induces neuritogenesis and axon/filopodium outgrowth; however its mechanism of action is still unresolved. We recently reported that the integrity of the transmembrane domains (TMDs) 2 and 4 are critical for M6a filopodia induction. There is also experimental data suggesting that M6a might be involved in synaptogenesis. In this regard, we have previously determined that M6a is involved in filopodia motility, a process that is described in the first step of the filopodial model for synaptogenesis. In this work we analyzed the possible involvement of M6a in synaptogenesis and spinogenesis, and evaluated the effect of two non-synonymous SNPs present in the coding region of TMD2-GPM6A in these processes. The results showed that endogenous M6a colocalized with both, pre-synaptic (synaptophysin) and post-synaptic (NMDA-R1), markers along of neuronal soma and dendrites. M6a-overexpressing neurons displayed an increased number of synaptophysin and NMDA-R1 puncta and, also, an increased number of colocalization puncta between both markers. Conversely, the number of synaptic puncta markers in neurons expressing nsSNP variants was similar to those of control neurons. Overexpression of M6a is accompanied by an increase in spine density, particularly in mature spines, as compared with neurons expressing mGFP or GPM6A nsSNP variants. Taken together, these results suggest that M6a contributes positively to spine and, likely, synapse formation.
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PMID:Evidence for a role of glycoprotein M6a in dendritic spine formation and synaptogenesis. 2779 98

Single point mutations or variations in the expression of the gene encoding the neuronal glycoprotein M6a have been associated with psychiatric disorders such as Alzheimer's disease, depression and schizophrenia. In cultured neurons, M6a positively contributes to neurite extension, axon guidance, filopodia/spine outgrowth, and synapse formation. The endocytic processes of neuronal membrane proteins are linked to the differentiation, growth, signaling and plasticity of neurons. However, the roles of M6a and the precise mechanisms through which M6a internalizes and recycles back to the neuronal membrane are unknown. Here, by using a controlled in vitro assay, we showed that if 30-40% of M6a is endocytosed, the number of synapses in hippocampal neurons decreases. When re-establishing the levels of M6a at the cell surface, the number of synapses returned to normal values. M6a internalization involves clathrin-coated pits, probably by association between the adaptor protein 2 and the 251YEDI254 "tyrosine-based" motif located within the C-tail of M6a. Upon endocytosis, M6a is sorted to early endosome antigen 1- and Rab5-positive endosomes and then sorted back to the cell surface via Rab11-positive endosomes or to degradation via Rab7 and, finally LAMP-1-positive endosomes. Our results demonstrated that the levels of M6a at the cell surface modified the formation/maintenance of synapses, without altering the protein levels of synaptophysin or N-methyl-D-aspartate receptor type-1. This novel mechanism might be relevant during neuronal development, pruning and/or many of the neurological disorders in which the number of synapses is affected.
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PMID:The Membrane Glycoprotein M6a Endocytic/Recycling Pathway Involves Clathrin-Mediated Endocytosis and Affects Neuronal Synapses. 2897 85

Nowadays, great efforts are made to gain insight into the molecular mechanisms that underlie structural neuronal plasticity. Moreover, the identification of signaling pathways involved in the development of psychiatric disorders aids the screening of possible therapeutic targets. Genetic variations or alterations in GPM6A expression are linked to neurological disorders such as schizophrenia, depression, and Alzheimer's disease. GPM6A encodes the neuronal surface glycoprotein M6a that promotes filopodia/spine, dendrite, and synapse formation by unknown mechanisms. A substantial body of evidence suggests that the extracellular loops of M6a command its function. However, the proteins that associate with them and that modulate neuronal plasticity have not been determined yet. To address this question, we generated a chimera protein that only contains the extracellular loops of M6a and performed a co-immunoprecipitation with rat hippocampus samples followed by TMT/MS. Here, we report 72 proteins, which are good candidates to interact with M6a's extracellular loops and modify its function. Gene ontology (GO) analysis showed that 63% of the potential M6a's interactor proteins belong to the category "synapse," at both sides of the synaptic cleft, "neuron projections" (51%) and "presynapse" (49%). In this sense, we showed that endogenous M6a interacts with piccolo, synaptic vesicle protein 2B, and synapsin 1 in mature cultured hippocampal neurons. Interestingly, about 28% of the proteins left were related to the "myelin sheath" annotation, suggesting that M6a could interact with proteins at the surface of oligodendrocytes. Indeed, we demonstrated the (cis and trans) interaction between M6a and proteolipid protein (PLP) in neuroblastoma N2a cells. Finally, the 72 proteins were subjected to disease-associated genes and variants screening by DisGeNET. Apart from the diseases that have already been associated with M6a, most of the proteins are also involved in "autistic disorder," "epilepsy," and "seizures" increasing the spectrum of disorders in which M6a could play a role. Data are available via ProteomeXchange with identifier PXD017347.
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PMID:Identification of Potential Interacting Proteins With the Extracellular Loops of the Neuronal Glycoprotein M6a by TMT/MS. 3284 94