The synaptic vesicle proteins synapsin I and synaptophysin (protein P38) are concentrated both in efferent and afferent nerve endings of the skeletal muscle

Synapsin I and synaptophysin (protein p38) are 2 major protein components of the membranes of small synaptic vesicles of virtually all presynaptic nerve endings. Synapsin I, a phosphoprotein regulated by both Ca2+ and cAMP, is a peripheral protein of the cytoplasmic surface of the vesicle membrane. It is thought to anchor the vesicle surface to the cytoskeleton of the terminal and to play a regulatory role in neurotransmitter release. Synaptophysin is an intrinsic transmembrane glycoprotein. We report here that both proteins are present and concentrated also in afferent nerve endings, which provide the sensory innervation of the skeletal muscle and of the tendon. The distribution of both antigens in sensory nerve endings is consistent with their localization on the microvesicles that have been described in such endings. Thus, our results suggest the existence of important biochemical, and possibly functional, similarities between small synaptic vesicles of presynaptic nerve endings and microvesicles of sensory endings. Such findings provide new clues to the understanding of the physiology of sensory endings

A cAMP-binding ectoprotein in the yeast Saccharomyces cerevisiae

tides 10, 593-595

P-29 - A NOVEL TYROSINE-PHOSPHORYLATED MEMBRANE-PROTEIN PRESENT IN SMALL CLEAR VESICLES OF NEURONS AND ENDOCRINE-CELLS

BAUMERT M, TAKEI K, HARTINGER J, et al. P-29 - A NOVEL TYROSINE-PHOSPHORYLATED MEMBRANE-PROTEIN PRESENT IN SMALL CLEAR VESICLES OF NEURONS AND ENDOCRINE-CELLS. JOURNAL OF CELL BIOLOGY. 1990;110(4):1285-1294

LOCALIZATION OF RAB5 TO SYNAPTIC VESICLES IDENTIFIES ENDOSOMAL INTERMEDIATE IN SYNAPTIC VESICLE RECYCLING PATHWAY

Fischer von Mollard G, STAHL B, WALCHSOLIMENA C, et al. LOCALIZATION OF RAB5 TO SYNAPTIC VESICLES IDENTIFIES ENDOSOMAL INTERMEDIATE IN SYNAPTIC VESICLE RECYCLING PATHWAY. EUROPEAN JOURNAL OF CELL BIOLOGY. 1994;65(2):319-326.After exocytosis, synaptic vesicles rapidly endocytose and recycle but little is known about the molecular mechanisms involved. Rab5 is a ubiquitous low molecular weight GTP-binding protein required for endosomal fusion in fibroblasts. We have now raised polyclonal and monoclonal antibodies to rat Rab5 and show that in rat brain. Rab5 is a major synaptic vesicle protein. Immunoisola tion of vesicular organelles from brain with antibodies to either Rab3A and Rab5 as small GTP-binding proteins or with synaptophysin as general synaptic vesicle marker demonstrates that there are overlapping populations of synaptic vesicles containing either Rab5 or Rab3A or both, suggesting a stage-specific association of these low-molecular weight GTP-binding proteins with synaptic vesicles. Our data provide the first biochemical evidence that synaptic vesicle recycling involves an endosomal intermediate similar to that of the receptor mediated endocytosis pathway