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Calcium Channel, Voltage-dependent, T Type, Alpha-1i Subunit OKDB#: 2600
 Symbols: CACNA1I Species: human
 Synonyms: KIAA1120  Locus:


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General Comment NCBI Summary: Voltage-dependent calcium channels control the rapid entry of Ca(2+) into a variety of cell types and are therefore involved in both electrical and cellular signaling. T-type channels, such as CACNA1I, are activated by small membrane depolarizations and can generate burst firing and pacemaker activity.[supplied by OMIM] Several transcript variants have been found for this gene, but the full-length nature of only two of them has been determined.
General function Channel/transport protein
Comment
Cellular localization Plasma membrane
Comment
Ovarian function Steroid metabolism
Comment
Expression regulated by
Comment
Ovarian localization Granulosa
Comment Agoston A, et al reported two types of calcium channels in human ovarian endocrine cells: involvement in steroidogenesis. Nature, regulation, and functional role of ion channels of human ovarian endocrine cells are not well known. In our present study, we show two types of voltage-activated Ca(2+) currents (I(Ca)) in cultured human luteinized granulosa cells (GCs), as assessed by whole-cell patch-clamp experiments. Electrophysiological properties, namely low threshold of activation, pronounced time-dependent inactivation, slow and voltage-dependent deactivation kinetics, insensitivity to SNX-482, and high sensitivity to Ni(2+), defined the predominant I(Ca) as a T-type Ca(2+) current (I(Ca.T)). In 4% of cells a Ni(2+)-insensitive I(Ca) was measured alone or together with I(Ca.T). This Ca(2+) current was high voltage activated and highly sensitive to dihydropyridine, indicative of an L-type Ca(2+) current. RT-PCR analysis demonstrated the presence of mRNA coding for alpha(1)-subunits of two different Ca(2+) channels (T-type Ca(v)3.2 and L-type Ca(v)1.2) in GCs. In addition, these two types were detected in the human corpus luteum by RT-PCR (Ca(v)3.2) and immunohistochemistry (Ca(v)1.2). Although stimulation of cultured GCs with human chorionic gonadotropin did not change the characteristics of recorded I(Ca.T), it markedly increased the percentage of cells displaying I(Ca) from 29 to 63% and significantly increased (2.2-fold) the density of I(Ca.T). Furthermore, the stimulatory effect of human chorionic gonadotropin on progesterone production was diminished by pharmacological blockage of I(Ca.T) by Ni(2+) or flunarizine. Thus, our study provides evidence that human GCs in vivo and in vitro express T- and L-type Ca(2+) channels and that the Ca(v)3.2 (also called alpha(1H)) isoform is involved in a fundamental endocrine function of these cells.
Follicle stages
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Phenotypes
Mutations 0 mutations
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created: Sept. 15, 2004, 8:44 a.m. by: hsueh   email:
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last update: Sept. 15, 2004, 8:44 a.m. by: system    email:



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