SCAMP-37, A NEW MARKER WITHIN THE GENERAL CELL-SURFACE RECYCLING SYSTEM

Secretory carrier membrane proteins (SCAMPs) are widely distributed as components of post-Golgi membranes that function as recycling carriers to the cell surface. In fibroblasts, SCAMPs are concentrated in compartments involved in the endocytosis and recycling of celt surface receptors while in neurons and other cell types having regulated transport pathways, SCAMPs are also components of regulated carriers (synaptic vesicles, secretion granules and transporter vesicles). Their presence in multiple pathways distinguishes them from proteins (e.g. recycling cell surface receptors and synaptic vesicle proteins) which are concentrated in selected pathways. The SCAMPs also do not appear to reside beyond the boundaries of these pathways. This distribution suggests that SCAMPs are general markers of membranes that function in cell surface recycling. The primary sequence of SCAMP 37 reveals a novel polypeptide containing a series of structural motifs, including a calcium binding domain, a leucine zipper and two zinc ringers. The very broad tissue distribution, subcellular localization and sequence analysis all predict that SCAMPs play a fundamental role in cell surface recycling.