Molecular cloning and characterization of a putative voltage-insensitive calcium channel from non-excitable cells.
Item
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Title
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Molecular cloning and characterization of a putative voltage-insensitive calcium channel from non-excitable cells.
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Identifier
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AAI9432356
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identifier
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9432356
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Creator
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Ma, Yongsheng.
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Contributor
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Adviser: Andrew R. Marks
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Date
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1994
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Language
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English
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Publisher
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City University of New York.
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Subject
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Biology, Molecular | Agriculture, General | Biology, Cell
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Abstract
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Voltage gated Ca{dollar}\sp{lcub}2+{rcub}{dollar} channels have been cloned and characterized from excitable cells including nerve and muscle. Analysis of the primary structures of these channels have shown that they share a common structural motif consisting of 24 putative transmembrane segments organized in four repeats. Voltage sensors are proposed to reside at the fourth transmembrane segment of each repeat. These channels play important roles in many cellular functions including propagation of action potentials, muscle excitation-contraction coupling, maintenance of electrical activity, excitation-secretion coupling, and neurotransmitter regulation. In non-excitable cells, a Ca{dollar}\sp{lcub}2+{rcub}{dollar} channel has been postulated to exist based on electrophysiological studies (Gardner, 1990). The primary structure of this Ca{dollar}\sp{lcub}2+{rcub}{dollar} channel in a non-excitable cell is, however, not known. In this study, murine erythroleukemia cells (MELC) were used as a model for non-excitable cells and the calcium dependence of HMBA-induced MELC differentiation was demonstrated (Gillo et al., 1993). Whole-cell patch clamp did not detect voltage-gated Ca{dollar}\sp{lcub}2+{rcub}{dollar} channels in MELC cells (Gillo et al., 1993). However, MELC did exhibit a dihydropyridine (DHP)-sensitive calcium influx (Gillo et al., 1993). This finding stimulated us to clone and characterize a putative Ca{dollar}\sp{lcub}2+{rcub}{dollar} channel from MELC and the resulting clone was termed the MELC Ca{dollar}\sp{lcub}2+{rcub}{dollar} channel (MELC-CC). Analysis of the MELC-CC cDNA sequence revealed that it is a novel isoform of the cardiac voltage-gated Ca{dollar}\sp{lcub}2+{rcub}{dollar} channel. The MELC-CC is truncated at its amino terminus, lacking the four putative transmembrane segments designated IS1 through IS4. This finding suggests that the MELC-CC could have physiological properties that differ from those in the voltage-dependent Ca{dollar}\sp{lcub}2+{rcub}{dollar} channel of excitable cells.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
