Different Susceptibility of Small and Large Human Tenascin-C Isoforms to Degradation by Matrix Metalloproteinases

doi:10.1074/jbc.270.15.8650

Different Susceptibility of Small and Large Human Tenascin-C Isoforms to Degradation by Matrix Metalloproteinases (*)

From the (1) Laboratory of Cell Biology, Istituto Nazionale per la Ricerca sul Cancro, Viale Benedetto XV,10, 16132 Genoa, Italy and
(2) Strangeways Research Laboratory, Worts' Causeway, Cambridge, CB1 4RN, United Kingdom

** To whom correspondence should be addressed. Tel.: 39-10-3534901; Fax: 39-10-352855; E-mail: lzardi{at}CISI.unige.it.

Abstract

Two major tenascin-C (TN-C) isoforms are generated by the alternative splicing of the pre-mRNA. The large isoform contains seven extra type three repeats that, by contrast, are omitted in the small TN-C isoform. The large TN-C isoform is mainly expressed at the onset of cellular processes that entail active cell migration, proliferation, or tissue remodeling such as occur in neoplasia, wound healing, and during development. Thus, the large TN-C isoform seems to be a specific component of the provisional extracellular matrix. Here we have studied the degradation of the large and small TN-C isoforms by matrix metalloproteinases (MMPs) 2, 3, 7, and 9. Among these proteolytic enzymes only MMP-7 can degrade the small TN-C isoform removing the NH₂-terminal knob. The large TN-C isoform shows the same MMP-7-sensitive site adjacent to the NH₂-terminal sequence, but is further degraded in the splicing area where three fibronectin-like type III repeats are completely digested. Moreover, the large TN-C isoform is degraded by MMP-2 and MMP-3 which completely digest a single type III repeat inside the splicing area. By contrast, the large TN-C isoform is resistant to MMP-9 digestion. The results show that the presence of the spliced sequence introduces new protease-sensitive sites in the large TN-C isoform.

Footnotes

↵^§ Supported by a Wellcome Trust Travelling Fellowship.
↵^¶ Supported by the Arthritis and Rheumatism Council United Kingdom.
↵* This study was supported in part by funds of the Associazione Italiana per la Ricerca sul Cancro (AIRC) and the Consiglio Nazionale delle Ricerche (CNR), “Progetto Finalizzato: Applicazioni Cliniche Della Ricerca Oncologica.” The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵¹ The abbreviations used are:

TN-C

tenascin-C

FN

fibronectin

MMP

matrix metalloproteinase

PAGE

polyacrylamide gel electrophoresis

EGF

epidermal growth factor

ECM

extracellular matrix

mAb

monoclonal antibody

BHK

baby hamster kidney.