Differential modulation of SERCA2 isoforms by calreticulin.
In Xenopus laevis oocytes, overexpression of calreticulin suppresses inositol 1,4,5-trisphosphate-induced Ca2+ oscillations in a manner consistent with inhibition of Ca2+ uptake into the endoplasmic reticulum. Here we report that the alternatively spliced isoforms of the sarcoendoplasmic reticulum Ca2+-ATPase (SERCA)2 gene display differential Ca2+ wave properties and sensitivity to modulation by calreticulin. We demonstrate by glucosidase inhibition and site-directed mutagenesis that a putative glycosylated residue (N1036) in SERCA2b is critical in determining both the selective targeting of calreticulin to SERCA2b and isoform functional differences. Calreticulin belongs to a novel class of lectin ER chaperones that modulate immature protein folding. In addition to this role, we suggest that these chaperones dynamically modulate the conformation of mature glycoproteins, thereby affecting their function.
John
L M
LM
Department of Biomedical Engineering, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
Lechleiter
J D
JD
Camacho
P
P
D017485:1-Deoxynojirimycin / Q000494:pharmacology; D017398:Alternative Splicing / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001621:Betahistine / Q000378:metabolism*; D002118:Calcium / Q000032:analysis; D002135:Calcium-Binding Proteins / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000737:chemistry*; D037282:Calreticulin; D004721:Endoplasmic Reticulum / Q000201:enzymology*; D005959:Glucosidases / Q000037:antagonists & inhibitors; D049452:Green Fluorescent Proteins; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007527:Isoenzymes / Q000502:physiology; D008164:Luminescent Proteins / Q000235:genetics; D008845:Microinjections; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009865:Oocytes / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics; D012261:Ribonucleoproteins / Q000502:physiology*; D014982:Xenopus laevis
D002135:Calcium-Binding Proteins; D037282:Calreticulin; D007527:Isoenzymes; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D012261:Ribonucleoproteins; D049452:Green Fluorescent Proteins; D017485:1-Deoxynojirimycin; D015544:Inositol 1,4,5-Trisphosphate; D005959:Glucosidases; D000252:Calcium-Transporting ATPases; D002118:Calcium; D001621:Betahistine