EGF-Like domain of tenascin-C is proapoptotic for cultured smooth muscle cells.
OBJECTIVE
Based on our previous observations on the expression of Tenascin-C (Tn-C) in human atherosclerotic plaques and its colocalization with macrophages, we explored whether Tn-C undergoes fragmentation and the potential pathobiological significance of this fragmentation.


RESULTS
Using cultured human smooth muscle cells (SMCs), we found that Tn-C upregulates expression of matrix metalloproteinases (MMPs). Western blot analysis revealed that Tn-C substrate is fragmented and most of the cleavage products have fibronectin-like and epidermal growth factor-like (EGF-like) domains of Tn-C. One fragment that contains an EGF-like domain was found in some human atherosclerotic plaques. Cell culture studies revealed that the recombinant EGF-like domain inhibits growth, induces apoptosis of SMCs in a dose-dependent, time-dependent, and caspase-dependent manner, and activates caspase-3 before SMC detachment. Conversely, the caspase inhibitor z-YVAD.cmk, serum, and protease inhibitors blocked cell apoptosis conferred by the EGF-like domain. In addition, these inhibitors blocked EGF-like domain-induced caspase-3 activation. In contrast to this EGF-like domain, intact Tn-C, its fibronectin-like, and its fibrinogen-like domains were inactive.


CONCLUSIONS
Together with our previous observations, our data suggest that Tn-C upregulates MMP expression that cleaves Tn-C into fragments containing the EGF-like domain. This domain has proapoptotic activity for SMCs.
Wallner
Kurt
K
Atherosclerosis Research Center, Division of Cardiology, and Burns and Allen Research Institute, Cedars-Sinai Medical Center, and UCLA School of Medicine, Los Angeles, Calif 90048, USA.
Li
Chen
C
Shah
Prediman K
PK
Wu
Kai-Jin
KJ
Schwartz
Stephen M
SM
Sharifi
Behrooz G
BG
D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D002339:Carotid Arteries / Q000737:chemistry / Q000166:cytology; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002460:Cell Line; D006224:Cricetinae; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D004815:Epidermal Growth Factor / Q000737:chemistry; D006801:Humans; D061965:Matrix Metalloproteinase Inhibitors; D020782:Matrix Metalloproteinases / Q000096:biosynthesis; D008647:Mesocricetus; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D032389:Myocytes, Smooth Muscle / Q000166:cytology / Q000187:drug effects*; D009842:Oligopeptides / Q000494:pharmacology; D010446:Peptide Fragments / Q000737:chemistry / Q000494:pharmacology; D011480:Protease Inhibitors / Q000494:pharmacology; D020033:Protein Isoforms / Q000737:chemistry / Q000494:pharmacology; D017434:Protein Structure, Tertiary; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D019311:Staurosporine / Q000494:pharmacology; D019063:Tenascin / Q000737:chemistry / Q000494:pharmacology*
D000590:Amino Acid Chloromethyl Ketones; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D061965:Matrix Metalloproteinase Inhibitors; C078131:N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide; D009842:Oligopeptides; D010446:Peptide Fragments; D011480:Protease Inhibitors; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D019063:Tenascin; C459419:benzyloxycarbonyltyrosyl-alanyl-valyl-aspartyl chloromethyl ketone; D003609:Dactinomycin; D004815:Epidermal Growth Factor; C002101:chymostatin; C505407:CASP3 protein, human; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases; D020782:Matrix Metalloproteinases; D019311:Staurosporine