Transmembrane Signaling

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This project aimed at elucidation of signal transduction pathway from membrane receptors to physiological cellular responses.1. First Year (1989) : We studied signal transduction pathway in muscle cells.(1) Involvement of lyotonin in contraction of smooth muscles was studied.(2) Involvement of inositol metabolites in Ca transients in skeletal muscles was studied.(3) Fura-2 visualization of Ca transients in bull-frog skeletal muscles was done.The threshold for caffeine stimulation for Ca release was measured to be 1-2 mM.2. Second Year (1990) : We studied exocrine glands and anti-channel drugs.(1) In colonic goblet cells, okadaic acid blocked the late part of the secretory and Ca responses induced by muscarinic stimulation. Thus, phosphorylation of muscarinic receptors mediates desensitization of these cellular responses.(2) Exocytotic responses in salivary gland of tupai were clearly detected by DIC microscopy. Water secretion was visualized as periodical movements of the apical membra … More ne of acinar cells. Muscarinic stimulants and ATP were effective but BETA stimulants were not in inducing secretory responses in the sublingual gland.(3) Toosendainine was found to suppress the Ca channel activity in NG108 cells.(4) A neurotoxin that specifically blocks the Na channel in insects was purified from the scorpion venom.3. Third Year (1991) : Stimulation-secretion coupling in tupai salivary gland and glutamate responses in retinal horizontal cells were studied.(1) Either various activators of protein kinase C nor K-depolarization were not effective in inducing secretory response in the salivary gland. These suggested that transmembrane signaling in salivary gland is mediated by a 2nd messenger system other than A-kinase and C-kinase systems.(2) Kinate-induced currents were studied in horizontal cells. Dopamine modulated the kinate current in a dose-dependent manner. Haroperidol suppressed the effect of dopamine on the kinate current. These modulatory effects are thought to arise from alteration of cGMP messenger system. Less