EVIDENCE FOR N-GLYCOSYLATION AND UBIQUITINATION OF THE PROLACTIN RECEPTOR EXPRESSED IN A BACULOVIRUS-INSECT CELL SYSTEM

The molecular mass of the rabbit prolactin receptor (rbPRLR) deduced f rom cDNA cloning is 66 kDa. However, the molecular mass of the full-le ngth receptor expressed in the insect Sf9 cells was found to be 94 kDa . In order to explain this discrepancy, we analyzed the possible post- translational modifications of the PRLR. Sf9 cells were infected with recombinant baculoviruses in the presence of tunicamycin, an inhibitor of N-glycosylation. Results showed that an additional approximate to 9 kDa of the extracellular domain could be attributed to the N-glycosy lation and another additional approximate to 20 kDa covalent modificat ion occurred in the cytoplasmic part of the receptor. Western blot ana lysis, using anti-ubiquitin antibodies, revealed that the rbPRLR was u biquitinated in its cytoplasmic domain.