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Neural cell adhesion molecule (NCAM), also called CD56, is a homophilic binding glycoprotein expressed on the surface of neurons, glia, skeletal muscle and natural killer cells. NCAM has been implicated as having a role in cell–cell adhesion,〔(Pathology Outlines )〕 neurite outgrowth, synaptic plasticity, and learning and memory. ==Forms, domains and homophilic binding== NCAM is a glycoprotein of Immunoglobulin (Ig) superfamily. At least 27 alternatively spliced NCAM mRNAs are produced, giving a wide diversity of NCAM isoforms. The three main isoforms of NCAM vary only in their cytoplasmic domain: * NCAM-120kDa (GPI anchored) * NCAM-140kDa (short cytoplasmic domain) * NCAM-180kDa (long cytoplasmic domain) The extracellular domain of NCAM consists of five immunoglobulin-like (Ig) domains followed by two fibronectin type III (FNIII) domains. The different domains of NCAM have been shown to have different roles, with the Ig domains being involved in homophilic binding to NCAM, and the FNIII domains being involved signaling leading to neurite outgrowth. Homophilic binding occurs between NCAM molecules on opposing surfaces (''trans-'') and NCAM molecules on the same surface (''cis-'')1. There is much controversy as to how exactly NCAM homophilic binding is arranged both in trans- and ''cis-''. Current models suggest ''trans-'' homophilic binding occurs between two NCAM molecules binding antiparallel between all five Ig domains or just IgI and IgII. ''cis-'' homophilic binding is thought to occur by interactions between both IgI and IgII, and IgI and IgIII, forming a higher order NCAM multimer. Both ''cis-'' and ''trans-'' NCAM homophilic binding have been shown to be important in NCAM “activation” leading to neurite outgrowth. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Neural cell adhesion molecule」の詳細全文を読む スポンサード リンク
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