Perlecan up-regulation of FRNK suppresses smooth muscle cell proliferation via inhibition of FAK signaling.
We previously reported that fully assembled basement membranes are nonpermissive to smooth muscle cell (SMC) replication and that perlecan (PN), a basement membrane heparan sulfate proteoglycan, is a dominant effector of this response. We report here that SMC adhesion to basement membranes, and perlecan in particular, up-regulate the expression of focal adhesion kinase-related nonkinase (FRNK), a SMC-specific endogenous inhibitor of FAK, which subsequently suppresses FAK-mediated, ERK1/2-dependent growth signals. Up-regulation of FRNK by perlecan is actively and continuously regulated. Relative to the matrix proteins studied, the effects are unique to perlecan, because plating of SMCs on several other basement membrane proteins is associated with low levels of FRNK and corresponding high levels of FAK and ERK1/2 phosphorylation and SMC growth. Perlecan supports SMC adhesion, although there is reduced cell spreading compared with fibronectin (FN), laminin (LN), or collagen type IV (IV). Despite the reduction in cell spreading, we report that perlecan-induced up-regulation of FRNK is independent of cell shape changes. Growth inhibition by perlecan was rescued by overexpressing a constitutively active FAK construct, but overexpressing kinase-inactivated mutant FAK or FRNK attenuated fibronectin-stimulated growth. These data indicate that perlecan functions as an endogenously produced inhibitor of SMC growth at least in part through the active regulation of FRNK expression. FRNK, in turn, may control SMC growth by downregulating FAK-dependent signaling events.
Walker
Heather A
HA
Department of Pediatrics, Renal Division, University of Colorado Health Sciences Center, Denver 80262, USA.
Whitelock
John M
JM
Garl
Pamela J
PJ
Nemenoff
Raphael A
RA
Stenmark
Kurt R
KR
Weiser-Evans
Mary C M
MC
D000818:Animals; D002455:Cell Division / Q000502:physiology*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019812:Heparan Sulfate Proteoglycans / Q000378:metabolism*; D006801:Humans; D051379:Mice; D032389:Myocytes, Smooth Muscle / Q000502:physiology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation
D019812:Heparan Sulfate Proteoglycans; C071927:perlecan; C113183:FAK-related nonkinase; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496050:PTK2 protein, human; C496051:Ptk2 protein, mouse; C496052:Ptk2 protein, rat