Molecular Mechanism and Signal Transduction for Salivary Secretion

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The purpose of this study is to investigate the molecular mechanism of salivary secretion, which is indicated by serial phenomena including synthesis of salivary protein, sorting, intracellular transport of secretory granules and membrane fusion at the exocytosis through the signal transduction. Gap junctions which possess a signal function for salivary secretion are composed of proteins termed as connexins. It is well known that different types of connexins exist in various tissues and organs. Using western blotting, immunohistochemistry and immunocytochemistry, we demonstrated that both connexins 26 and 32 were Iocated between acinar cells, but connexin 43 was distributed between myoepithelial cells in the salivary glands. These may suggest that both connexins 26 and 32 participate in signal transduction for salivary secretion in acinar cells, but connexin 43 is correlated to signaling for contraction of myoepithelial cells (J Histochem Cytochem 44 : 49-56,1996 ; Europ J Morphol 34 : … More 197-202,1996). We also clarified that connexins 26 and 32 constituted the same gap junction in the salivary gland (Acta Histochem Cytochem, in press). The expression of connexins 32 and 43 was investigated in the developing salivary glands employing PCR,in situ hybridization and immunohistochemistry (Europ J Morphol, in press). We studied not only the localization of actin filaments and proteins constituting tight junction such as ZO-1 or occludin but also the expression of clathlin participating endocytosis and a membrane-fusion associated protein (synaptophysin) in acinar cells during secretion using immunohistochemistry, immunocytochemistry and confocal laser scanning microscope. There was a close relationship between the localization of actin filaments and ZO-1 or Occludin. Clathrin was located at the periphery of the intracellular canalicula 10 or 30 minutes after IPR stimulation. This may indicate that endocytosis of secretory-granule-membrane occur immediately after the secretion (manuscript, in preparation). Less