Expression and characterization of a very low density lipoprotein receptor variant lacking the O-linked sugar region generated by alternative splicing

J Biochem. 1998 Oct;124(4):747-55. doi: 10.1093/oxfordjournals.jbchem.a022175.

Abstract

The very low density lipoprotein receptor (VLDLR) gene contains an exon encoding a region of clustered serine and threonine residues immediately outside the membrane-spanning sequence, and this region has been proposed to be the site of clustered O-linked carbohydrate chains. Two forms of VLDLR transcripts, with and without the O-linked sugar region, are generated through alternative splicing. Reverse transcription polymerase chain reaction with RNAs from various rabbit tissues revealed that the VLDLR transcript with the O-linked sugar region (type-1 VLDLR) is the major transcript in heart and muscle, while the VLDLR transcript without the O-linked sugar region (type-2 VLDLR) predominates in non-muscle tissues, including cerebrum, cerebellum, kidney, spleen, adrenal gland, testis, ovary, and uterus. Hamster fibroblasts expressing type-2 VLDLR bound with relatively low affinity to beta-migrating very low density lipoprotein compared with type-1 VLDLR-transfected cells. In contrast, the internalization, dissociation, and degradation of the ligand were not significantly impaired in either type of VLDLR-transfected cell. The receptor proteins in type-2 VLDLR-transfected cells underwent rapid degradation and accumulated in the culture medium, while those in type-1 VLDLR-transfected cells were stable and resistant to proteolytic cleavage. Analysis of the O-linked sugars of both types of transfected cells suggested that the O-linked sugar region is the major site for O-glycosylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing
  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Cricetinae
  • Female
  • Genetic Variation*
  • Glycosylation
  • Humans
  • Male
  • Molecular Sequence Data
  • Muscle, Skeletal / metabolism
  • Myocardium / metabolism
  • Organ Specificity
  • Protein Processing, Post-Translational
  • Rabbits
  • Receptors, LDL / biosynthesis
  • Receptors, LDL / chemistry*
  • Receptors, LDL / genetics*
  • Recombinant Proteins / biosynthesis
  • Recombinant Proteins / chemistry
  • Reverse Transcriptase Polymerase Chain Reaction
  • Serine
  • Threonine
  • Transcription, Genetic*
  • Transfection

Substances

  • Receptors, LDL
  • Recombinant Proteins
  • VLDL receptor
  • Threonine
  • Serine