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Updated: Aug 6, 2026

Primary Culture of Adult Rat Heart Myocytes
Published on: June 16, 2009
A region of calpastatin domain L that reprimes cardiac L-type Ca2+ channels
Etsuko Minobe1, Li-Ying Hao, Zahangir A Saud
1Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, Sakuragaoka 8-35-1, Kagoshima 890-8544, Japan.
Abstract:
Calpastatin, an endogenous inhibitor of calpain, is composed of domain L and four repetitive homologous domains 1-4. Domains 1-4 inhibit calpain, whereas domain L partially reprimes L-type Ca2+ channels for voltage-gated activation. In the present study, the effects on Ca2+ channel activity of four isoforms and a series of fragments of calpastatin domain L were investigated in guinea-pig ventricular myocytes with the patch-clamp method. With one exception, all the isoforms and fragment peptides that contained amino acid residues 54-64 of domain L reprimed the Ca2+ channels to comparable levels (9-15% of control activity) to those observed previously with a full-length form of calpastatin. These results suggest that the region containing amino acid residues 54-64 (EGKPKEHTEPK) is responsible for the Ca2+ channel repriming function of calpastatin domain L.
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