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This Article Full Text Full Text (PDF) All Versions of this Article: 577/2/513    most recent jphysiol.2006.117440v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Park, J.-Y. Articles by Lee, J.-H. Search for Related Content PubMed PubMed Citation Articles by Park, J.-Y. Articles by Lee, J.-H. Related Collections Cellular

¹ Department of Life Science
² Interdisciplinary Program of Biotechnology, Sogang University, Shinsu-dong, Seoul 121-742, Korea
³ Department of Physiology and Institute of Basic Medical Science, Yonsei University Wonju College of Medicine, Ilsan-Dong 162, Wonju, Kangwon-Do, Korea
⁴ National Institute on Aging, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA

T-type Ca²⁺ channels play essential roles in numerous cellular processes. Recently, we reported that phorbol-12-myristate-13-acetate (PMA) potently enhanced the current amplitude of Ca_v3.2 T-type channels reconstituted in Xenopus oocytes. Here, we have compared PMA modulation of the activities of Ca_v3.1, Ca_v3.2 and Ca_v3.3 channels, and have investigated the underlying mechanism. PMA augmented the current amplitudes of the three T-type channel isoforms, but the fold stimulations and time courses differed. The augmentation effects were not mimicked by 4-PMA, an inactive stereoisomer of PMA, but were abolished by preincubation with protein kinase C (PKC) inhibitors, indicating that PMA augmented T-type channel currents via activation of oocyte PKC. The stimulation effect on Ca_v3.1 channel activity by PKC was mimicked by endothelin when endothelin receptor type A was coexpressed with Ca_v3.1 in the Xenopus oocyte system. Pharmacological studies combined with fluorescence imaging revealed that the surface density of Ca_v3.1 T-type channels was not significantly changed by activation of PKC. The PKC effect on Ca_v3.1 was localized to the cytoplasmic II–III loop using chimeric channels with individual cytoplasmic loops of Ca_v3.1 replaced by those of Ca_v2.1.

(Received 18 July 2006; accepted after revision 25 September 2006; first published online 28 September 2006)
Corresponding author J.-H. Lee: Department of Life Science, Sogang University, Shinsu-dong, Seoul 121-742, Korea. Email: jhleem{at}sogang.ac.kr

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