Regulation of calreticulin expression during induction of differentiation in human myeloid cells. Evidence for remodeling of the endoplasmic reticulum.
Induction of differentiation of HL-60 human myeloid cells profoundly affected expression of calreticulin, a Ca(2+)-binding endoplasmic reticulum chaperone. Induction with Me(2)SO or retinoic acid reduced levels of calreticulin protein by approximately 60% within 4 days. Pulse-chase studies indicated that labeled calreticulin decayed at similar rates in differentiated and undifferentiated cells (t(12) approximately 4.6 days), but the biosynthetic rate was <10% of control after 4 days. Differentiation also induced a rapid decline in calreticulin mRNA levels (90% reduction after 1 day) without a decrease in transcript stability (t(12) approximately 5 h). Nuclear run-on analysis demonstrated rapid down-regulation of gene transcription (21% of control at 2 h). Differentiation also greatly reduced the Ca(2+) content of the cells (25% of control), although residual Ca(2+) pools remained sensitive to thapsigargin, ionomycin, and inositol trisphosphate. Progressive decreases were also observed in levels of calnexin and ERp57, whereas BiP/GRP78 and protein disulfide isomerase were only modestly affected. Ultrastructural studies showed a substantial reduction in endoplasmic reticulum content of the cells. Thus, terminal differentiation of myeloid cells was associated with decreased endoplasmic reticulum content, selective reductions in molecular chaperones, and diminished intracellular Ca(2+) stores, perhaps reflecting an endoplasmic reticulum remodeling program as a prominent feature of granulocytic differentiation.
Clark
Robert A
RA
Department of Medicine, South Texas Veterans Health Care System and University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA. clarkra@uthscsa.edu
Li
Sen-Lin
SL
Pearson
Doran W
DW
Leidal
Kevin G
KG
Clark
Joshua R
JR
Denning
Gerene M
GM
Reddick
Robert
R
Krause
Karl-Heinz
KH
Valente
Anthony J
AJ
D002135:Calcium-Binding Proteins / Q000235:genetics*; D037282:Calreticulin; D002454:Cell Differentiation / Q000502:physiology*; D002460:Cell Line; D004721:Endoplasmic Reticulum / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D018922:HL-60 Cells; D006801:Humans; D007700:Kinetics; D018832:Molecular Chaperones / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012261:Ribonucleoproteins / Q000235:genetics*; D013463:Sulfuric Acid Esters / Q000494:pharmacology; D013997:Time Factors; D014158:Transcription, Genetic / Q000187:drug effects; D014212:Tretinoin / Q000494:pharmacology
D002135:Calcium-Binding Proteins; D037282:Calreticulin; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D018832:Molecular Chaperones; D012333:RNA, Messenger; D012261:Ribonucleoproteins; D013463:Sulfuric Acid Esters; D014212:Tretinoin; C007482:dimethyl sulfate