A Major Second Messenger Mediator of Electrophorus electricus Electric Tissue is CaM Kinase II

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• 作者：Gotter ; Anthony L. ; Kaetzel ; Marcia A. ; Dedman ; John R.
• 关键词：Electrophorus electricus ; calmodulin-dependent protein kinase ; membrane excitability ; peptide inhibitors
• 刊名：Comparative Biochemistry and Physiology -- Part A: Physiology
• 出版年：1997
• 出版时间：September, 1997
• 年：1997
• 卷：118
• 期：1
• 页码：81-91
• 全文大小：1.76 M

文摘

Electric tissue of the electric eel, Electrophorus electricus, has been used extensively as a model system for the study of excitable membrane biochemistry and electrophysiology. Membrane receptors, ion channels, and ATPases utilized by electrocytes are conserved in mammalian neurons and myocytes. In this study, we show that Ca²⁺ predominates as the major mediator of electric tissue phosphorylation relative to cyclic AMP and cyclic GMP-induced phosphorylation. Mastoparan, a calmodulin inhibitor peptide, and a peptide corresponding to the pseudosubstrate region of mammalian calmodulin-dependent protein kinase II (CaMKII (281–302)) attenuated Ca²⁺-dependent phosphorylation in a dose-dependent manner. These experiments demonstrated that calmodulin-dependent protein kinase II activity predominates in electric tissue. The Electrophorus kinase was purified by a novel affinity chromatography procedure utilizing Ca²⁺/calmodulin-dependent binding to the CaMKII (281–302) peptide coupled to Sepharose. The purified 51 kDa calmodulin-dependent protein kinase II demonstrated extensive autophosphorylation and exhibited a 3- to 4-fold increase in Ca²⁺-independent activity following autophosphorylation. Immunofluorescent localization experiments demonstrated calmodulin to be abundant in electrocytes, particularly subjacent to the plasma membrane. Calmodulin-dependent protein kinase II had a punctate distribution indicating that it may be compartmentalized by association with vesicles or the cytoskeleton. As the primary mediator of phosphorylation within electric tissue, CaM kinase II may be critical for the regulation of the specialized electrophysiological function of electrocytes.