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

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Abstract
Versican is an extracellular matrix proteoglycan produced by many cells. Although versican is generally known as a large chondroitin sulfate proteoglycan (CSPG), the smallest splice variant, V3, consists only of the amino- and carboxy-terminal globular domains and is therefore predicted to be a small glycoprotein, lacking CS chains. The large size, negative charge, and ability of versican variants to form pericellular coats with hyaluronan are responsible for many of its effects. V3, lacking the large size and high charge density, but retaining the hyaluronan-binding domain of the larger isoforms, may have different effects on cell phenotype. To determine whether V3 alters cell phenotype, Fisher rat arterial smooth muscle cells (ASMCs), which express the larger CSPG versican splice forms (V0 and V1) were retrovirally transduced with the rat V3 cDNA. Northern analysis for versican RNAs confirmed that cells transduced with V3 retrovirus, but not cells tranduced with the empty vector, expressed RNA of the size expected for V3/neor bicistronic RNA. V3 overexpressing cells were more spread on tissue culture plastic, had a smaller length-to-breadth ratio and were more resistant to release from the culture dish by trypsin. Interference reflection microscopy of sparsely plated cells showed larger areas of close contact between the V3 expressing cells and the coverslip, in comparison to control cells. Focal contacts in the periphery of V3 expressing cells were larger. Growth and migration studies revealed that V3 transduced cells grow slower and migrate a shorter distance in a scratch wound assay. The increased adhesion and the inhibition of migration and proliferation resulting from V3 overexpression are 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. J. Cell. Physiol. 190: 38–45, 2002.

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