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Cerebral cavernous malformation 2 FERM domain C-lobe CCM2 (also called malcavernin; C7orf22/chromosome 7 open reading frame 22; OSM) along with CCM1 and CCM3 constitutes a set of proteins which when mutated are responsible for cerebral cavernous malformations, an autosomal dominant neurovascular disease characterized by cerebral hemorrhages and vascular malformations in the central nervous system. CCM2 plays many functional roles. CCM2 functions as a scaffold involved in small GTPase Rac-dependent p38 mitogen-activated protein kinase (MAPK) activation when the cell is under hyperosmotic stress. It associates with CCM1 in the signalling cascades that regulate vascular integrity and participates in HEG1 (the transmembrane receptor heart of glass 1) mediated endothelial cell junctions. CCM proteins also inhibit the activation of small GTPase RhoA and its downstream effector Rho kinase (ROCK) to limit vascular permeability. CCM2 mediates TrkA-dependent cell death via its N-terminal PTB domain in pediatric neuroblastic tumours. CCM2 possesses an N-terminal PTB domain and a C-terminal Karet domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.
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