Incomplete endoplasmic reticulum (ER) retention in immature thymocytes as revealed by surface expression of "ER-resident" molecular chaperones.
The folding and assembly of nascent proteins in the endoplasmic reticulum (ER) is assisted by molecular chaperones that are themselves retained within the ER. We now report that a number of different ER proteins, including molecular chaperones, are selectively expressed on the surface of immature thymocytes, but their surface expression is extinguished upon further differentiation. Escape from the ER is only possible for newly synthesized ER proteins before they become permanently retained. Thus, the cellular process of ER retention is incomplete in immature thymocytes and provides an explanation for surface expression of partial receptor complexes that transduce differentiative signals during thymic development.
Wiest
D L
DL
Experimental Immunology Branch, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Bhandoola
A
A
Punt
J
J
Kreibich
G
G
McKean
D
D
Singer
A
A
D015153:Blotting, Western; D017252:CD3 Complex / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000378:metabolism; D037281:Calnexin; D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism*; D002478:Cells, Cultured; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000378:metabolism*; D005434:Flow Cytometry; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D018832:Molecular Chaperones / Q000378:metabolism*; D011233:Precipitin Tests; D017510:Protein Folding; D013601:T-Lymphocytes / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology
D017252:CD3 Complex; D002135:Calcium-Binding Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; C034241:ribophorin; D037281:Calnexin