Expression of calcium channel subunits in the normal and diseased human myocardium.
We investigated the expression of alpha1 and beta subunits of the L-type Ca2+ channel on the protein level in cardiac preparations from normal human heart ventricles and from the hypertrophied septum of patients with hypertrophic obstructive cardiomyopathy (HOCM). 1,4-Dihydropyridine (DHP) binding and immunorecognition by polyclonal antibodies directed against the C-terminal amino acid sequences of the beta2 and beta3 subunits were used for detection and quantification of alpha1, beta2, and beta3 subunits. Bmax of high-affinity DHP binding was 35 +/- 2 fmol/mg protein in HOCM and 20 +/- 2 fmol/mg protein in normal human hearts (P<0.05). In rabbit hearts the anti-beta2 subunit antibody immunoprecipitated 80% of the total amount of DHP-labeled Ca2+ channels present in the assay. Under identical experimental conditions 25% of labeled Ca2+ channels were recovered in the immunoprecipitates of both normal and HOCM ventricles. A similar partial immunoprecipitation was observed in pig hearts. Immunoblot analysis demonstrated that the beta2 subunit was associated with the DHP receptor/Ca2+ channel in cardiac muscle of rabbit, pig, and human heart. In neither of these purified cardiac Ca2+ channels was the beta3 subunit isoform detected. Our results suggest that both alpha1 and beta2 subunit expression is upregulated in HOCM in a coordinate manner.
Haase
H
H
Max-Delbruck Center for Molecular Medicine, Berlin, Germany.
Kresse
A
A
Hohaus
A
A
Schulte
H D
HD
Maier
M
M
Osterziel
K J
KJ
Lange
P E
PE
Morano
I
I
D000595:Amino Acid Sequence; D001665:Binding Sites; D015220:Calcium Channels / Q000032:analysis*; D020746:Calcium Channels, L-Type; D002312:Cardiomyopathy, Hypertrophic / Q000378:metabolism*; D004095:Dihydropyridines / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009206:Myocardium / Q000737:chemistry*
D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D004095:Dihydropyridines; C038806:1,4-dihydropyridine