Versican, the major chondroitin sulfate proteoglycan (CSPG) of the vessel wall (Wight, T. N., The Vascular Extracellular Matrix. In: V., Fuster, R. Ross, and E. J. Topol (eds.), Atherosclerosis and Coronary Artery Disease, pp. 421-440. New York, N.Y.: Raven Press, 1996), is distinguished by a number of important structural features (Margolis, R. U. and Margolis, R. K., Aggrecan-Versican-Neurocan Family of Proteoglycans, Methods Enzymol., 245:105-126, 1994; Zimmermann, D. R. and Ruoslahti, E., Multiple Domains of the Large Fibroblast Proteoglycan, Versican, EMBO J., 8:2975-2981, 1989). The central extended region with attached glycosaminoglycan (GAG) chains confers space filling and viscoelastic properties on the matrix. The chondroitin sulfate chains are highly negatively charged and are believe to contribute anti-adhesive properties to the molecule. This domain is flanked by amino- and carboxy terminal globular domains, through which versican binds to other matrix molecules. The amino-terminal domain is responsible for the binding of versican to the glycosaminoglycan hyaluronan (HA) (LeBaron, R. G., Zimmermann, D. R., and Ruoslahti, E., Hyaluronate Binding Properties of Versican, J. Biol. Chem., 267:10003-10010, 1992). Together, these molecules can form large pericellular coats (Evanko, S. P., Angello, J. C., and Wight, T. N., Formation of Hyaluronan- and Versican-Rich Pericellular Matrix is Required for Proliferation and Migration of Vascular Smooth Muscle Cells, Arterioscler Thromb Vasc Biol., 19: 1004-13, 1999), which are anchored to cells via HA receptors, and which may inhibit the interaction of the cell with other cells or molecules. The carboxy terminal globular domain consists of EGF-like, lectin-like, and compliment-regulatory protein-like domains (Zimmermann, D. R. and Ruoslahti, E., Multiple Domains of the Large Fibroblast Proteoglycan, Versican, EMBO J., 8:2975-2981, 1989). The EGF-like domain has been shown to be pro-proliferative and the lectin-like domain binds tenascin-R and fibulin-1 (Zhang, Y., Cao, L., Yang, B. L., and Yang, B. B., The G3 Domain of Versican Enhances Cell Proliferation via Epidermial Growth Factor-like Motifs, J Biol. Chem., 273:21342-51, 1998; Aspberg, A., Binkert, C., and Ruoslahti, E., The Versican C-type Lectin Domain Recognizes the Adhesion Protein Tenascin-R, Proc. Natl. Acad. Sci. USA, 92:10590-10594, 1995; Aspberg, A., Adam, S., Kostka, G., Timpl, R., and Heinegard, D., Fibulin-1 is a Ligand for the C-type Lectin Domains of Aggrecan and Versican, J. Biol. Chem., 274:20444-20449, 1999).
More recently, versican has been shown to be synthesized as multiple splice variants (Zako, M., Shinomura, T., Ujita, M., Ito, K., and Kimata, K., Expression of PG-M(V3), an Alternatively Spliced form of PG-M without a Chondroitin Sulfate Attachment Region in Mouse and Human Tissues, J. Biol. Chem., 270:3914-3918, 1995; Dours-Zimmermann, M. T. and Zimmermann, D. R., A Novel Glycosaminoglycan Attachment Domain Identified in Two Alternative Splice Variants of Human Versican, J. Biol. Chem., 269:32992-32998, 1994; Ito, K., Shinomura, T., Zako, M., Ujita, M., and Kimata, K., Multiple Forms of Mouse PG-M, a Large Chondroitin Sulfate Proteoglycan Generated by Alternative Splicing, J. Biol. Chem., 270:958-965, 1995). Three of these variants (V0 (Accession No. U16306), V1 (Accession No. X15998), and V2 (Accession No. U26555)), include one or both of the GAG attachment domains and thus differ in the length of the central domain and are predicted to also differ in the number of CS chains attached (Dours-Zimmermann, M. T. and Zimmermann, D. R., A Novel Glycosaminoglycan Attachment Domain Identified in Two Alternative Splice Variants of Human Versican, J. Biol. Chem., 269:32992-32998, 1994; Ito, K., Shinomura, T., Zako, M., Ujita, M., and Kimata, K., Multiple Forms of Mouse PG-M, a Large Chondroitin Sulfate Proteoglycan Generated by Alternative Splicing, J. Biol. Chem., 270:958-965, 1995). A fourth variant, V3, lacks both of the GAG attachment exons and is thus predicted to be a glycoprotein, but not a proteoglycan, and to comprise only the two globular domains (Zako, M., Shinomura, T., Ujita, M., Ito, K., and Kimata, K., Expression of PG-M(V3), an Alternatively Spliced Form of PG-M without a Chondroitin Sulfate Attachment Region in Mouse and Human Tissues, J. Biol. Chem., 270:3914-3918, 1995).
We showed earlier that vascular smooth muscle cells express the originally cloned versican isoform, V1, both in vivo and in vitro, and that versican expression by smooth muscle cells in vitro is regulated by PDGF, TGF-b, and IL-1 (Yao, L. Y., Moody, C., Schonherr, E., Wight, T. N., and Sandell, L. J., Identification of the Proteoglycan Versican in Aorta and Smooth Muscle Cells by DNA Sequence Analysis, In Situ Hybridization and Immunohistochemistry, Matrix Biol., 14:213-225, 1994; Schonherr, E., Jarvelainen, H. T., Sandell, L. J., and Wight, T. N., Effects of Platelet-Derived Growth Factor and Transforming Growth Factor-beta 1 on the Synthesis of a Large Versican-like Chondroitin Sulfate Proteoglycan by Arterial Smooth Muscle Cells, J. Biol. Chem., 266: 17640-17647, 1991; manuscript in preparation). More recently, we have shown that cultured aortic smooth muscle cells can express the V0 and V3 isoforms as well (Lemire, J., Braun, K., Maurel, P., Kaplan, E., Schwartz, S., and Wight, T., Versican/PG-M Isoforms in Vascular Smooth Muscle Cells, Arterioscler. Thromb. Vasc. Biol., 19:1630-1639, 1999). Importantly, however, whereas functions have been demonstrated for V0 and V1 isoforms, no function has been demonstrated for V3. We are interested in the function of versican in vascular tissue, and in particular, in whether the small V3 variant may have a different role.