Versican/PG-M isoforms in vascular smooth muscle cells

The expression of increased amounts of proteoglycans in the extracellular m atrix may play a role in vascular stenosis and lipid retention. The large c hondroitin sulfate proteoglycan versican is synthesized by vascular smooth muscle cells (SMCs), accumulates during human atherosclerosis and restenosi s, and has been shown to bind LDLs. We recently demonstrated that adult rat aortic SMCs express several versican mRNAs. Four versican splice variants, V0, V1, V2, and V3, have recently been described, which differ dramaticall y in length. These variants differ in the extent of modification by glycosa minoglycan chains, and V3 may lack glycosaminoglycan chains. In this study, we characterized versican RNAs from rat SMCs by cloning, sequencing, and h ybridization with domain-specific probes. DNA sequence was obtained for the V3 isoform, and for a truncated V0 isoform. By hybridization of polyadenyl ated RNA with domain-specific probes, we determined that the V0, V1, and V3 isoforms are present in vascular SMCs. We confirmed the presence of the V3 isoform in polyadenylated RNA and in RT-PCR products by hybridization with an oligonucleotide that spans the splice junction between the hyaluronan-b inding domain and the epidermal growth factor-like domain. In addition, a n ovel splice variant was cloned by PCR amplification from both rat and human SMC RNA. This appears to be an incompletely spliced variant, retaining the final intron. PCR analysis shows that this intron can be retained in both V1 and V3 isoforms. The predicted translation product of this variant would have a different carboxy-terminus than previously described versican isofo rms.