Most strikingly, there was no immunoreactivity in BALB/c mouse brain with either OX7 or 7C8 antibodies, although in brain tissue from AKR mice, immunoreactivity was present that comigrated with rat Thy-1. the synapse. Our understanding of the molecular mechanisms involved in secretory vesicle dynamics has advanced substantially in the past 10 yr with the identification of many of the molecular components of secretory vesicles. Results from reconstitution of Golgi transport (Rothman, 1987), yeast secretion GANT 58 mutants (Kaiser and Schekman, 1990), and biochemical characterization of synaptic vesicles (Sdhof et al., 1993; Bajjalieh and Scheller, 1995) all point to the presence of common molecular components that carry out membrane fusion. For example, a generalized version of the SNARE1 hypothesis (S?llner et al., 1993) suggests that a precisely choreographed interplay between synaptic vesicle proteins, plasma membrane proteins, and cytoplasmic proteins results in Ca2+-stimulated membrane fusion. However, the specific details of many of the processes and molecular components involved in vesicle dynamics remain poorly defined. Neurons and endocrine cells are highly specialized to carry out regulated secretion from membrane-bounded storage vesicles when an appropriate stimulus is applied. At least two unique types of regulated secretory vesicles coexist within neurons and endocrine cells; these organelles are typically referred to as small synaptic, Rabbit Polyclonal to ZDHHC2 or synaptic-like vesicles (SSVs) and large, dense-core vesicles (LDCVs). SSVs and LDCVs differ in a GANT 58 variety of physical and functional properties, including size, density, contents, membrane components, location within cells, GANT 58 biogenesis, and kinetics of release. Despite the differences, these two types of vesicles share many common properties, including transport to the vicinity of specialized release sites, close apposition to specialized sites around the plasma membrane, and the ability to fuse with the plasma membrane in a highly regulated manner, typically in response to an elevation in intracellular free Ca2+ concentration. A first step in the biochemical approach to understanding regulated secretion entails the identification of the components of the secretory vesicles. A considerable number of such proteins have now been recognized. These include the synaptotagmins (Matthew et al., 1981), SV2 (Buckley and Kelly, 1985), synaptophysin/P38 (Jahn et al., 1985; Wiedenmann and Franke, 1985), the synapsins (De Camilli and Greengard, 1986), synaptobrevin, (Trimble et al., 1988; Baumert et al., 1989), rab 3A (Fisher von Mollard et al., 1990), the cysteine string protein (Zinsmaier et al., 1990; Gunderson and Umbach, 1992), and synaptogyrin/P29 (Baumert et al., 1990; Stenius et al., 1995). These proteins are present in all GANT 58 SSVs irrespective of the specific neurotransmitter content (De Camilli and Jahn, 1990). Some, such as synaptotagmin and SV2, are found in both SSVs and LDCVs (Lowe et al., 1988), whereas others, such as synaptophysin and the synapsins, are associated predominantly or exclusively with SSVs (Navone et al., 1984; Navone et al., 1986). Although many of the synaptic GANT 58 vesicle proteins mentioned above were initially recognized only as uncharacterized proteins specifically associated with vesicles, considerable information has now been obtained about their interactions and possible functions (for review observe Sdhof, 1995). PC12 cells (Greene and Tischler, 1976) are neuroendocrine cells that contain both LDCVs that store and release catecholamines (Greene and Rein, 1977; Wagner, 1985) and small clear vesicles that contain ACh (Bauerfeind et al., 1993). The small clear vesicles of these and other neuroendocrine cells are biochemically very similar to the neuronal SSVs (Navone et al., 1986; Lowe et al., 1988; Obendorf et al., 1988; Johnston et al., 1989; Navone et al., 1989; Grote and Kelly, 1996). Based on the expectation that proteins, that play a fundamental role in regulated secretion should be found as components of both LDCVs and SSVs, we have searched for components found on both populations of regulated secretory vesicles in PC12 cells. We statement here our unexpected finding that one such protein is usually Thy-1, a glycosyl-phosphatidylinositol (GPI)Clinked.