The T-type Ca2+ channel is an important determinant of electrical activity and of Ca2+ influx in rat and human pancreatic beta-cells. We have identified and sequenced a cDNA encoding a T-type Ca2+ channel alpha1-subunit derived from INS-1, the rat insulin-secreting cell line. The sequence of the cDNA indicates a protein composed of 2,288 amino acids that shares 96.3% identity to alpha1G, the neuronal T-type Ca2+ channel subunit. The transmembrane domains of the protein are highly conserved, but the isoform contains three distinct regions and 10 single amino acid substitutions in other regions. Sequencing rat genomic DNA revealed that the alpha1-subunit we cloned is an alternative splice isoform of alpha1G. By using specific primers and reverse transcription-polymerase chain reaction, we demonstrated that both splice variants are expressed in rat islets. The isoform deduced from INS-1 was also expressed in brain, neonatal heart, and kidney. Functional expression of this alpha1G isoform in Xenopus oocytes generated low voltage-activated Ba2+ currents. These results provide the molecular biological basis for studies of function of T-type Ca2+ channels in beta-cells, which is where these channels may play critical roles in diabetes.
Skip Nav Destination
Article navigation
Abstract|
January 01 2000
Cloning of a T-type Ca2+ channel isoform in insulin-secreting cells.
H Zhuang;
H Zhuang
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
A Bhattacharjee;
A Bhattacharjee
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
F Hu;
F Hu
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
M Zhang;
M Zhang
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
T Goswami;
T Goswami
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
L Wang;
L Wang
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
S Wu;
S Wu
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
P O Berggren;
P O Berggren
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
M Li
M Li
Department of Pharmacology, College of Medicine, University of South Alabama, Mobile 36688, USA.
Search for other works by this author on:
Citation
H Zhuang, A Bhattacharjee, F Hu, M Zhang, T Goswami, L Wang, S Wu, P O Berggren, M Li; Cloning of a T-type Ca2+ channel isoform in insulin-secreting cells.. Diabetes 1 January 2000; 49 (1): 59–64. https://doi.org/10.2337/diabetes.49.1.59
Download citation file: