Cell surface-bound collagenase-1 and focal substrate degradation stimulatethe rear release of motile vascular smooth muscle cells

TO migrate in the vessel wall, smooth muscle cells (SMCs) must contend with abundant type I collagen. We investigated: the mechanisms used by human SM Cs to efficiently migrate on type I collagen, following stimulation with fi broblast growth factor-2 (FGF-2). FGF-a-stimulated migration was inhibited by a hydroxamic acid inhibitor of matrix metalloproteinases and by a neutra lizing anti-collagenase-1 antibody. Moreover, migration speed of SMCs plate d on mutant collagenase-resistant type I collagen was not increased by FGF- S. Time-lapse video analysis of unstimulated SMCs migrating on collagen rev ealed discrete phases of leading edge membrane extension and rear retractio n, the latter often after rupture of an elongated tail. FGF-2 stimulation y ielded a more synchronous, gliding motion with a collagenase-1-mediated dec rease in tail ripping. Surface labeling of SMCs with biotin followed by imm unoprecipitation revealed that a proportion of active collagenase-1, expres sed in response to FGF-2, was bound to the plasma membrane. Pericellular co llagen substrate cleavage-was verified by immunostaining for neoepitopes ge nerated by collagenase-1 action and was localized to discrete zones beneath the cell tail and the leading edge. These results identify a novel mechani sm by which SMC migration on collagen is enhanced, whereby rear release fro m the substrate is orchestrated by the localized actions of membrane-bound collagenase-1.