Overexpression of the V3 variant of versican alters arterial smooth musclecell adhesion, migration, and proliferation in vitro

Versican is an extracellular matrix proteoglycan produced by many cells. Al though versican is generally known as a large chondroitin sulfate proteogly can (CSPG), the smallest splice variant, V3, consists only of the amino- an d carboxyterminal globular domains and is therefore predicted to be a small glycoprotein, lacking CS chains. The large size, negative charge, and abil ity of versican variants to form pericellular coats with hyaluronan are res ponsible for many of its effects. V3, lacking the large size and high charg e density, but retaining the hyaluronan-binding domain of the larger isofor ms, may have different effects on cell phenotype. To determine whether V3 a lters cell phenotype, Fisher rat arterial smooth muscle cells (ASMCs), whic h express the larger CSPG versican splice forms (V0 and Vi) were retroviral ly transduced with the rat V3 cDNA. Northern analysis for versican RNAs con firmed that cells transduced with V3 retrovirus, but not cells tranduced wi th the empty vector, expressed RNA of the size expected for V3/neo(r) bicis tronic RNA. V3 overexpressing cells were more spread on tissue culture plas tic, had a smaller length-to-breadth ratio and were more resistant to relea se from the culture dish by trypsin. Interference reflection microscopy of sparsely plated cells showed larger areas of close contact between the V3 e xpressing cells and the coverslip, in comparison to control cells. Focal co ntacts in the periphery of V3 expressing cells were larger. Growth and migr ation studies revealed that V3 transduced cells grow slower and migrate a s horter distance in a scratch wound assay. The increased adhesion and the in hibition of migration and proliferation resulting from V3 overexpression ar e the opposites of the known and predicted effects of the other variants of versican. V3 may exert these effects through changes in pericellular coat formation, either by competing with larger isoforms for hyaluronan-binding, or by altering other components of the pericellular matrix. (C) 2002 Wiley -Liss, Inc.