Truncated β2 subunits increase membrane expression of LTCC subunits in A7r5 cells

Abstract

Listen

Translate article

Cytosolic Ca2+ is regulated by Ca2+ entry through L‐type calcium channels (LTCC) and release from intracellular Ca2+ stores via the IP3 receptors (IP3R) in vascular smooth muscle cells (VSMC). The β2 subunit of the LTCC is an intracellular chaperone that interacts with the α1C subunit via its beta interaction domain (BID) to regulate membrane localization and channel function. In order to alter assembly of the LTCC at the cell surface of VSMC, we used adenovirus constructs to overexpress either the β2 subunit (Full‐β2) or truncated β2 subunits lacking either the C‐, N‐terminus or both (N‐BID, C‐BID or BID, respectively) fused to GFP. Immunoblot analysis confirmed that Full‐β2 was primarily expressed in the membrane fraction while C‐BID and N‐BID expression at the membrane was reduced to 70% and 52%, respectively. BID was in the cytosol, like GFP. Full‐β2 significantly increased α1C subunit expression at the membrane, as did C‐BID and N‐BID. Membrane levels of α2 subunit were also increased by the 3 constructs. BID did not modify localization of the LTCC subunits. Membrane levels of IP3R were significantly increased only by Full‐β2. Our study showed that truncated β2 subunits can alter expression of the LTCC subunits at the cell surface and suggest that LTCC function could be regulated by these decoys. Development of VSMC‐specific constructs may represent a viable gene‐based treatment to regulate vascular reactivity.