Primary cultures of cardiac muscle cells as models for investigation of protein glycosylation
Primary cardiac cell cultures of newborn rats containing approximately 50% (by cell number) spontaneously contracting cardiomyocytes were used to study the role of protein N-glycosylation for the binding of dihydropyridine (DHP) to the voltage-dependent L-type calcium channel. This binding is not influenced by the accompanying non-muscle cells.
Exposure of the cells up to 6 μg/ml of the N-glycosylation inhibitor tunicamycin for a 44 h period resulted in a decrease of the specific DHP binding sites (Bmax) to 46.0 ± 17.2% of the untreated control. Similar effects were observed after enzymatic deglycosylation using N-glycosidase F (PNGase F). The results suggest that a posttranslational modification of parts of the cardiac L-type Ca++ channel by N-glycosylation is an important determinant for the binding of Ca++ antagonists of the DHP-type to the 1 subunit which itself is not glycosylated. The results suggest a participation of N glycosylation in the assembling of the subunits to the functional channel and/or its turnover. However, a possible effect of tunicamycin on the expression of the Ca channel as an alternative mechanism cannot be excluded. (Mol Cell Biochem 160/16141–46, 1996)
Key wordscalcium channel glycosylation glycoprotein cardiac muscle cells primary culture
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