Tetraspan vesicle membrane proteins: synthesis, subcellular localization and functional properties
Hübner K, Windoffer R, Hutter H, Leube RE, 2002
Tetraspan vesicle membrane proteins (NPs) are characterized by four transmembrane regions and cytoplasmically located end domains. They are ubiquitous and abundant components of vesicles in most, if not all, cells of multicellular organisms. TVP-containing vesicles shuttle between various membranous compartments and are localized in biosynthetic and endocytotic pathways. Based on gene organization and amino acid sequence similarities TVPs can be grouped into three distinct families that are referred to as physins, gyrins, and secretory carrier-associated membrane proteins (SCAMPs). In mammals synaptophysin, synaptoporin, pantophysin, and mitsugumin29 constitute the physins, synaptogyrin 1–4 the gyrins, and SCAMP1–5 the SCAMPs.
Members of each family are cell-type-specifically synthesized resulting in unique patterns of TVP coexpression and subcellular colocalization. TVP orthologs have been identified in most multicellular organisms, including diverse animal and plant species, but have not been detected in unicellular organisms. They are subject to protein modification, most notably to phosphorylation, and are part of multimeric complexes. Experimental evidence is reviewed showing that NPs contribute to vesicle trafficking and membrane morphogenesis.
Fluorescence microscopy of a transgenic Caenorhabditis elegans expressing a fluorescent synaptogyrin chimera consisting of the entire nematode synaptogyrin that is fused to the enhanced yellow fluorescent protein. The specific fluorescence is restricted to neurons including, most notably, the dorsal and ventral nerve cords and the pharyngeal nerve ring.