Ly. Hao et al., Calpastatin domain L is involved in the regulation of L-type Ca2+ channelsin guinea pig cardiac myocytes, BIOC BIOP R, 279(3), 2000, pp. 756-761
Citations number
25
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
We have found previously that L-type Ca2+ channel run-down in cell-free pat
ches is partially (10-28%) reversed by calpastatin (CS) and have suggested
that CS, an endogenous inhibitor of calpain, has a Ca2+-channel-regulating
function. CS is composed of repetitive domains 1-4 (calpain-inhibitory doma
in) and domain L (a domain whose function is unknown). We therefore investi
gated which domain of CS was involved in the regulation of Ca2+ channel act
ivity in guinea pig cardiac myocytes using the patch-clamp technique. After
the patches were excised into inside-out mode in basic internal solution,
the Ca2+ channel activity ran down to 0.45% of the control level recorded i
n the cell-attached mode. Application of human recombinant full-length CS (
25 muM) and domain L (25 muM) restored the Ca2+ channel activity to 13 and
19% of the control level, respectively, while the channel activity was not
restored by CS domain 1 (25 muM) (0.66%). Mouse CS domain XLL (25 muM), a c
omplex of domain XL and domain L, restored the calcium channel activity to
11% of the control level, These results suggested that the Ca2+-channel-reg
ulating function of CS is located in domain L, This study is the first desc
ription of the function of CS domain L. (C) 2000 Academic Press.