Changes in Elastin-Binding Proteins during the Phenotypic Transition of Rabbit Arterial Smooth Muscle Cells in Primary Culture

Abstract

Elastin, a major constituent of the media, may play an important role in the attachment, migration, and phenotypic properties of vascular smooth muscle cells (SMC). We examined binding proteins and binding sites on elastin in rabbit arterial SMC in primary culture. Freshly isolated cells on α-elastin underwent phenotypic transition from a contractile to a synthetic state after 5 days of culture under serum-deficient conditions (1% FBS) and began to proliferate after 6 days of culture (48 h later than on plastic dishes). SMC in the contractile state expressed two binding proteins (130 and 36 kDa), while the 130-kDa band was undetectable in cells in the synthetic state. The adhesion of freshly isolated cells and cells in the synthetic state to α-elastin was significantly inhibited by a monoclonal anti-elastin receptor antibody (BCZ-67). The synthetic peptide VGVAPG (Val-Gly-Val-Ala-Pro-Gly), which contains the recognition sequence for the elastin receptor, inhibited the adhesion of freshly isolated cells to α-elastin at 0.01-1 m M, but showed no inhibitory activity on the adhesion of cells in the synthetic state at 0.01 m M. These findings suggest that α-elastin suppresses the phenotypic transition of rabbit arterial SMC by interacting with the high-molecular-size (130 kDa) binding protein for a cell-binding sequence VGVAPG, while cells in the synthetic state can recognize α-elastin through interactions with the low-molecular-size (36 kDa) binding protein for the sequence VGVAPG.