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Transcriptional regulation of ?1H T-type calcium channel under hypoxia.

ABSTRACT: The low-voltage-activated T-type Ca(2+) channels play an important role in mediating the cellular responses to altered oxygen tension. Among three T-type channel isoforms, ?1G, ?1H, and ?1I, only ?1H was found to be upregulated under hypoxia. However, mechanisms underlying such hypoxia-dependent isoform-specific gene regulation remain incompletely understood. We, therefore, studied the hypoxia-dependent transcriptional regulation of ?1G and ?1H gene promoters with the aim to identify the functional hypoxia-response elements (HREs). In rat pulmonary artery smooth muscle cells (PASMCs) and pheochromocytoma (PC12) cells after hypoxia (3% O2) exposure, we observed a prominent increase in ?1H mRNA at 12 h along with a significant rise in ?1H-mediated T-type current at 24 and 48 h. We then cloned two promoter fragments from the 5'-flanking regions of rat ?1G and ?1H gene, 2,000 and 3,076 bp, respectively, and inserted these fragments into a luciferase reporter vector. Transient transfection of PASMCs and PC12 cells with these recombinant constructs and subsequent luciferase assay revealed a significant increase in luciferase activity from the reporter containing the ?1H, but not ?1G, promoter fragment under hypoxia. Using serial deletion and point mutation analysis strategies, we identified a functional HRE at site -1,173cacgc-1,169 within the ?1H promoter region. Furthermore, an electrophoretic mobility shift assay using this site as a DNA probe demonstrated an increased binding activity to nuclear protein extracts from the cells after hypoxia exposure. Taken together, these findings indicate that hypoxia-induced ?1H upregulation involves binding of hypoxia-inducible factor to an HRE within the ?1H promoter region.

SUBMITTER: Sellak H

PROVIDER: S-EPMC4187058 | biostudies-literature | 2014 Oct

REPOSITORIES: biostudies-literature

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Transcriptional regulation of α1H T-type calcium channel under hypoxia.

Sellak Hassan H Zhou Chun C Liu Bainan B Chen Hairu H Lincoln Thomas M TM Wu Songwei S

American journal of physiology. Cell physiology 20140806 7

The low-voltage-activated T-type Ca(2+) channels play an important role in mediating the cellular responses to altered oxygen tension. Among three T-type channel isoforms, α1G, α1H, and α1I, only α1H was found to be upregulated under hypoxia. However, mechanisms underlying such hypoxia-dependent isoform-specific gene regulation remain incompletely understood. We, therefore, studied the hypoxia-dependent transcriptional regulation of α1G and α1H gene promoters with the aim to identify the functio ...[more]

PMID: 25099734

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Transcriptional regulation of ?1H T-type calcium channel under hypoxia.

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Transcriptional regulation of α1H T-type calcium channel under hypoxia.

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