BOVINE AORTIC ENDOTHELIAL-CELLS EXPRESS A VARIANT OF THE VERY-LOW-DENSITY LIPOPROTEIN RECEPTOR THAT LACKS THE O-LINKED SUGAR DOMAIN

The very low density lipoprotein (VLDL) receptor is a member of the lo w density lipoprotein supergene family of receptors in which different ial splicing of mRNA has been reported. We present several lines of ev idence showing that bovine aortic endothelial cells exclusively expres s a VLDL receptor isoform that lacks the O-linked sugar domain i) West ern and receptor-associated protein (RAP) ligand blotting gave a singl e band of about 99 kDa in membrane extracts of bovine aortic endotheli al cells (BAEC), ii) Screening of the BAEC cDNA library with the previ ously characterized human VLDL receptor cDNA. as a probe gave several C-terminal-positive clones; all lacked the 84 nucleotides correspondin g to exon 16, Polymerase chain reaction (PCR) confirmed that VLDL rece ptor cDNA encoding exon 16 was absent from the library. iii) Reverse t ranscription (RT)-PCR analysis of the BAEC mRNA using a pair of oligon ucleotide primers that flank the deletion gave only one band of 136 nt . iv) Semiquantitative RT-PCR analysis showed that only the non-O-glyc osylated variant was expressed in BAEC, Cell-binding studies with anti bodies against the N-terminal domain showed that the BAEC VLDL recepto r is present at the plasma membrane, suggesting that the non-glycosyla ted variant could be functional. In addition, RT-PCR performed in bovi ne tissues showed that the variant containing the O-linked sugar domai n is preferentially expressed in heart, brain, and skeletal muscle, wh ereas the non-O-glycosylated spliced variant is found in all tissues a nalyzed.jlr Taken together these results suggest that the differential splicing of the VLDL receptor is cell- and tissue-specific and that t he functions of the receptor could depend on the cell type.