Expression and characterization of a very low density lipoprotein receptor variant lacking the O-linked sugar region generated by alternative splicing.
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.
Tohoku University Gene Research Center, Aoba, Sendai, 981-8555, Japan.
H
H
Iijima
M
M
Miyazawa
J
J
Sakai
K
K
Magoori
M R
MR
Ito
H
H
Suzuki
M
M
Nose
Y
Y
Kawarabayasi
T T
TT
Yamamoto
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D006224:Cricetinae; D005260:Female; D014644:Genetic Variation; D006031:Glycosylation; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009928:Organ Specificity; D011499:Protein Processing, Post-Translational; D011817:Rabbits; D011973:Receptors, LDL / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics*; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000737:chemistry; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012694:Serine; D013912:Threonine; D014158:Transcription, Genetic; D014162:Transfection
D011973:Receptors, LDL; D011994:Recombinant Proteins; C036053:VLDL receptor; D013912:Threonine; D012694:Serine