Characterization of pituitary calcium-activated, phospholipid-dependent protein kinase: redistribution by gonadotropin-releasing hormone
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Pituitary C kinase might be involved in signal-transduction mechanisms in Gn-RH action, in particular, and in other hypophysiotropic hormones, in general, which operate by means of stimulation of phosphoinositide turnover during which diacylglycerol is liberated.Abstract:
We report the presence in the rat pituitary of a calcium-activated, phospholipid-dependent protein kinase (C kinase), originally described by Takai et al. [Takai, Y., Kishimoto, A., Iwasa, Y., Kawahara, Y., Mori, T. & Nishizuka, Y. (1979) J. Biol. Chem. 254, 3692-3695]. Enzyme activity is absolutely dependent on the simultaneous presence of Ca2+ and phospholipid--in particular, phosphatidylserine. The presence of small amounts of unsaturated diacylglycerol greatly increases the apparent affinity of the enzyme for Ca2+ and phosphatidylserine. Pituitary C kinase is mostly soluble (70%) and partly particulate (30%). Although the soluble form of the enzyme can be detected in a crude cytosol preparation, the particulate form is detectable only after solubilization and anion-exchange chromatography. Administration of a gonadotropin-releasing hormone (Gn-RH) agonist analog, [D-Ser(But)6]des-Gly10-Gn-RH-N-ethylamide, to ovariectomized rats resulted in elevated serum luteinizing hormone levels (245%) accompanied by a decrease in the cytosolic form of the enzyme (60%) and an increase in the particulate form (300%) after 5 min. This apparent activation of the particulate form seems to result from translocation of a soluble C kinase to the membrane. Several endogenous substrate proteins for C kinase ranging from 16 to 100 kDa were identified in pituitary cytosol. Pituitary C kinase might be involved in signal-transduction mechanisms in Gn-RH action, in particular, and in other hypophysiotropic hormones, in general, which operate by means of stimulation of phosphoinositide turnover during which diacylglycerol is liberated.read more
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Journal ArticleDOI
Studies of gonadotropin-releasing hormone (GnRH) action using GnRH receptor-expressing pituitary cell lines.
TL;DR: GnRH Action in GH3 cells transfected with the GnRH Receptor (GGH3 cells) and regulation of GnRHR regulation are described.
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The molecular mechanism of action of gonadotropin releasing hormone (GnRH) in the pituitary.
TL;DR: This chapter focuses on the molecular basis of GnRH action, regulation of gonadotropic responsiveness, and stimulus-LH release coupling at the gonadotropin.
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Molecular mechanism of gonadotropin releasing hormone action. II. The effector system.
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Intracellular responses to gonadotropin-releasing hormone in a clonal cell line of the gonadotrope lineage.
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