Multiple cleavage sites for polymeric immunoglobulin receptor

Abstract

SUMMARYHuman polymeric immunoglobulin receptor (pIgR) was expressed in baby hamster kidney (BHK) cells using a recombinant vaccinia virus transfection system. Cleavage of pIgR on the cell surface was partially inhibited by the proteinase inhibitor, leupeptin. We addressed the question whether some particular regions of pIgR could affect the efficient cleavage of this molecule, with the following results: (1) a mutant lacking the entire cytoplasmic region resulted in release of secretory component (SC) into the culture supernatant much faster than wild-type; (2) a pIgR mutant lacking the entire extracellular domain 6, the region containing the susceptible cleavage sites, could be cleaved and released as a mutant SC. The transport kinetics of this mutant between endoplasmic reticulum (ER) and Golgi or Golgi and the cell surface was equivalent to wild-type pIgR. Our results indicate that although the main cleavage site is in domain 6, at least one other cleavage site may exist.

Polymeric immunoglobulin receptor

“…Most newly synthesized ∆CL mutant was secreted in the culture media, and no mutant pIgR was detected in the cell lysates (67). Our results further suggest that the cytoplasmic deletion mutant of pIgR was released from the cells immediately after its synthesis and that the cytoplasmic portion of pIgR has a plasma membrane retention signal (67).…”

“…5, ∆CL mutant) and observed that fSC release was drastically inhibited. These results indicate that domain 6 of pIgR has an intrinsic signal for the pIgR to be recognized and cleaved by proteolytic enzyme (67). The 12 amino acids spanning from Pro589 to Asp600 are highly conserved in several species and are the putative cleavage site of pIgR (31).…”

“…This mutant was transfected to baby hamster kidney (BHK) cells by using a recombinant vaccinia virus-mediated transfection method (68), and the secretion of fSC was compared with that of wild-type pIgR. Most newly synthesized ∆CL mutant was secreted in the culture media, and no mutant pIgR was detected in the cell lysates (67). Our results further suggest that the cytoplasmic deletion mutant of pIgR was released from the cells immediately after its synthesis and that the cytoplasmic portion of pIgR has a plasma membrane retention signal (67).…”

“…We generated whole cytoplasmicdeletion (∆CP) and whole domain 6 deletion (∆CL) mutants. PM, plasma membrane cleaved and released (67). We transfected BHK cells with pIgR cDNA, and expression of pIgR was confirmed by Western blotting and pulse-chase experiments (67).…”

“…PM, plasma membrane cleaved and released (67). We transfected BHK cells with pIgR cDNA, and expression of pIgR was confirmed by Western blotting and pulse-chase experiments (67). Using this expression system, we attempted to express a deletion mutant lacking domain 6 of the extracellular portion (Fig.…”