High impact information on calr

• We examined the role of the luminal Ca(2+)-binding protein calreticulin (CRT) in IP3-mediated Ca2+ signaling by using Ca2+ wave activity as a sensitive Ca2+ release assay [1].
• Deletion mutagenesis demonstrated that CRT inhibition was mediated by the high affinity-low capacity Ca(2+)-binding domain, which contributes little to Ca2+ storage [1].
• This novel function of CRT in intracellular Ca2+ signaling may be regulated by Ca2+ occupancy of the high affinity binding site [1].
• 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 [2].
• Calreticulin belongs to a novel class of lectin ER chaperones that modulate immature protein folding [2].

Biological context of calr

• Strong expression of the calreticulin gene in the liver of Rana rugosa tadpoles, but not adult frogs [3].
• These results suggest that the expression of the CLT gene is tissue-dependent in the frog, R. rugosa, and that CLT probably functions biochemically in liver cells even when its gene expression is low [3].
• Using rat CLT cDNA as a probe, a 2.4-kilobase frog cDNA clone was isolated from a frog liver cDNA library [3].

Anatomical context of calr

• 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 [2].
• Calreticulin (CRT) is a highly conserved Ca(2+)-binding protein that resides in the lumen of the endoplasmic reticulum (ER) [4].
• Identification of calreticulin isoforms in the central nervous system [5].
• Immunostaining showed that CLT was distributed in the cytoplasm of liver cells [3].

Associations of calr with chemical compounds

• Overexpression of CRT inhibited repetitive IP3-induced Ca2+ waves [1].
• The cDNA encoded 419 amino acids including an 18-residue NH2-terminal signal sequence that was 76% homologous to the rat CLT sequence and was 84% homologous to the partial sequence of Xenopus laevis CLT (Treves et al. [1992] Biochem. J. 287:579-581) [3].

Analytical, diagnostic and therapeutic context of calr

• 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 [2].
• Furthermore, CLT was recognized by Western blot analysis of total proteins in the liver of adult frogs [3].
• CLT with M(r) = 52 kDa, estimated by SDS-PAGE, was purified from frog livers [3].
• Northern blot analysis indicated that the CLT mRNA level was very high in the liver of tadpoles, but extremely low in adult frogs [3].

References