Calnexin endoplasmic reticulum

Mayer TU, Braun T, Jentsch, S (1998) Role of the proteasome in membrane extraction of a short-lived ER-transmembrane protein. EMBO ] 17 3251-3257 McCracken AA, Brodsky JL (1996) Assembly of ER-associated protein degradation in vitro dependence on cytosol, calnexin, and ATP. J Cell Biol 132 291-298 McDonald HB, Byers B (1997) A proteasome cap subunit required for spindle pole body duplication in yeast. J Cell Biol 137 539-553 McGee TP, Cheng HH, Kumagai H, Omura S, Simoni RD (1996) Degradation of 3-hydroxy-3-methylg utaryl-CoA reductase in endoplasmic reticulum membranes is accelerated as a result of increased susceptibility to proteolysis. J Biol Chem 271 25630-25638... 

R. G., Role of A-linked polymannose oligosaccharides in targeting glycoproteins for endoplasmic reticulum-associated degradation. Cell. Mol. Life Sci. 61,1025-1041, 2004 Bedard, K., Szabo, E., Michalak, M., and Opas, M., Cellular functions of endoplasmic reticulum chaperones calreticulin, calnexin, andERp57, Int. Rev. Cytol. 245, 91-121, 2005 Ito, Y, Hagihara,... 

There is evidence supporting a role for hepatic damage by intravascular proteases in the pathogenesis of neonatal hepatic disease, as reviewed in the previous edition of this textbook,The AAT deposits in the hepatic endoplasmic reticulum do not bind normally to calnexin, one of the chaperones for protein synthesis and release it is known that proteolytic enzymes reduce the activity of intracellular, membrane-bound proteins involved in metabolic processes. An additional component in congenital and neonatal hepatic disease may be exposure to maternal estrogens, which increase susceptibility to damage from hepatitis viral infections and some toxins. 

I-type CRDs derived from the immunoglobulin fold, (5)calnexin and calreticulin, which bind to N-linked oligosaccharides and retain misfolded glycoproteins in the endoplasmic reticulum, (6) the P-type lectins, which bind mannose-6-phosphate moieties, and (7)the R-type lectins, which contain CRDs similar to those found in ricin. 

Tatu, U., and Helenius, A. (1997). Interactions between newly synthesized glycoproteins, calnexin and a network of resident chaperones in the endoplasmic reticulum./. Cell Biol. 136, 555-565. 

Hebert, D. N., Foellmer, B., and Helenius, A. (1995). Glucose trimming and reglu-cosylation determine glycoprotein association with calnexin in the endoplasmic reticulum. Cell81, 425-433. 

Kearse, K P., Williams, D. B., and Singer, A. (1994). Persistence of glucose residues on core oligosaccharides prevents association ofTCRa andTCR/3 proteins with calnexin and results specifically in accelerated degradation of nascent TCRa proteins within the endoplasmic reticulum. EMBO J. 13, 3678-3686. 

Van Leeuwen, J. E. M., and Kearse, K. P. (1996). The related molecular chaperones calnexin and calreticulin differentially associate with nascent T cell antigen receptor proteins within the endoplasmic reticulum. J. Biol. Chem. 271, 25345-25349. 

Fig. 3.3 FVIII biosynthesis. Signal peptide cleavage and asparagine (N)-linked glycosylation of the FVIII occurs after translation and translocation to the lumen of the endoplasmic reticulum (ER). Within the ER, the FVIII is folded, which requires binding to chaperone proteins. FVIII binds immunoglobulin-binding protein (BiP) at the A1 domain, and is released in an ATP-dependent step. Next, FVIII binds calnexin (CNX) and calreticulin (CRT) (not shown) at the B domain. Properly folded FVIII proteins are transported to the Golgi by chaperone proteins, LMANl and MCFD2 (not shown) for further processing LMANl also binds to the FVIII B domain. Incorrectly folded FVIII...

Fig. 4.6 Cellular localization of FAAFI in human keratinocytes. Co-localization of FAAFI with calnexin (marker to endoplasmic reticulum). Human keratinocytes (HaCaT cells) were co-stained with anti-FAAH (in green) and anti-calnexin (in red) antibodies. Superimposition of the two stainings (merge) revealed a vesicular region of the endoplasmic reticulum where FAAH and calnexin largely overlapped (yellow). Dot structures, where FAAH and calnexin co-localized, are indicated by the white arrows in the inset at the bottom of the merge panel. The remaining part of the reticulum, with lamellar appearence, did not display any colocalization of the two proteins. Courtesy of Dr. Sergio Oddi (University of Teramo, Italy)...

Snijders, A.J. Ho, S.C. Haase, V.H. Pillai, S. Bernards, A. A lymphocyte-specific Ltk tyrosine kinase isoform is retained in the endoplasmic reticulum in association with calnexin. J. Biol. Chem., 272, 1297-1301 (1997)... 

It often is required that one ensure the SDS-PAGE samples are evenly loaded. Calnexin, an endoplasmic reticulum protein, is used for this purpose. Indeed, in some cases the expression level of a protein of interest (e.g., UGTIAI) is normalized by the amount of calnexin in each sample. In our experience, however, a Western blot of calnexin usually produce no detectable variation among the membrane fractions of COS-1 cells. 

Endoplasmic reticulum Calnexin Rabbit a-calnexin-CT Transmembrane protein Stressgen Bioreagents (SPA-860, use at 1 1000)... 

Pilon M, Schekman R, Romisch K (1997) Sec6lp mediates export of a misfolded secretory protein from the endoplasmic reticulum to the cytosol for degradation. EMBO J 16 4540-4548 Pipe SW, Morris JA, Shah J, Kaufman RJ (1998) Differential interaction of coagulation factor VIII and factor V with protein chaperones calnexin and calreticulin. J Biol Chem 273 8537 8544 Plemper RK, Bohmler S, Bordallo J, Sommer T, Wolf DH (1997) Mutant analysis links the translocon and BiP to retrograde protein transport for ER degradation. Nature 388 891 895 Plemper RK, Deak PM, Otto RT, Wolf DH (1999) Re-entering the translocon from the lumenal side of the endoplasmic reticulum. Studies on mutated carboxypeptidase yscY species. FEBS Lett 443 241-245... 

Fig. 1. Alternative models of HCMV gpUS6 interaction with the transient TAP complex containing peptide-free MHC I molecules and ER-resident chaperones. According to a minimal model , gpUS6 binds directly to TAP itself left). The cofactor models depict scenarios in which gpUS6 does not bind physically to TAP but to a protein present in the TAP complex center) or gpUS6 recruits an unrelated molecule, e.g., calnexin, to TAP right), resulting in functional inactivation of peptide transport. ER, endoplasmic reticulum p2-microglobulin. See text for details...

Calnexin, Calreticulin and Glycoprotein Folding Within the Endoplasmic Reticulum... 

Rajagopalan, S., and Brenner, M.B. Calnexin Retains Unassembled Major Histocompatibility Complex Class I Free Heavy Chains in the Endoplasmic Reticulum J. Exp. Med. 1994 180, 407-412. 

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