Endoplasmic reticulum resident, immunoglobulin joining chain, can be secreted by perturbation of the calcium concentration in the endoplasmic reticulum.
We established a transient human joining (J)-chain gene expression system in the baby hamster kidney (BHK) cell. The J-chain was detected as a 29-kDa single band on Western blotting. Immunofluorescent staining of the transfectant revealed an exclusive localization of the J-chain in the endoplasmic reticulum (ER). Intracellular transport experiment revealed that incubating conditions favorable for vesicular stomatitis virus glycoprotein (VSV-G) transport did not allow the J-chain to exit from the ER. Analysis of glycosylation status of the J-chain in the transfectant was examined by tunicamycin treatment, endoglycosidase H digestion, and also by treatment with brefeldin A. It was found that an N-glycosylation consensus site of the J-chain was functional, and intracellular J-chain was endoglycosidase H sensitive. These results indicate that, in the absence of any immunoglobulin molecules, J-chain localizes exclusively in the ER. We also tested whether the J-chain could be exported from the ER by perturbing the Ca2+ concentration in the ER. Cultivation of the J-chain transfectant in the presence of ionomycin resulted in the time-dependent secretion of the J-chain. The secreted J-chain was modified by the Golgi resident glycosylation enzymes, indicating that the secreted J-chain passed through the normal exocytic pathway.
Department of Pathology, Nihon University School of Dentistry, Kanda Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan. asano-m@dent.nihon-u.ac.jp
Masatake
M
Asano
Yoshitaka
Y
Ogura
Nobuko
N
Takenouchi-Ohkubo
Hirotsugu
H
Chihaya
Wu
W
Chung-Hsing
Kenji
K
Ishikawa
Kunihiko
K
Kobayashi
Jean-Pierre
JP
Vaerman
Itaru
I
Moro
D000818:Animals; D020126:Brefeldin A / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D006224:Cricetinae; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism*; D006031:Glycosylation; D006801:Humans; D007144:Immunoglobulin J-Chains / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015759:Ionomycin / Q000494:pharmacology; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D013997:Time Factors; D014162:Transfection; D014415:Tunicamycin / Q000494:pharmacology; D014759:Viral Envelope Proteins / Q000235:genetics / Q000378:metabolism
C028391:G protein, vesicular stomatitis virus; D007144:Immunoglobulin J-Chains; D008562:Membrane Glycoproteins; D014759:Viral Envelope Proteins; D014415:Tunicamycin; D020126:Brefeldin A; D015759:Ionomycin; D017038:Mannosyl-Glycoprotein Endo-beta-N-Acetylglucosaminidase; D002118:Calcium