Calreticulin, mouse monoclonal, Cat# MCA-6C6

Calreticulin, mouse monoclonal, Cat# MCA-6C6



HeLa cell cultures were stained with MCA-6C6 antibody (red).  Calreticulin predominately localized in vesicles and the ER. Cells were counterstained with our chicken polyclonal antibody to Vimentin CPCA-Vim in green. Blue is a DNA stain.

 Western blot analysis of MCA-6C6 in HEK293 (lane1), 3T3 (lane2), SHSY-5Y (lane3) and  HeLa cells (lane4). The MCA-6C6 monoclonal binds strongly to calreticulin in 50 kDa.

Product name Anti-Calreticulin
Description Mouse Monoclonal to calreticulin.
Reference Code MCA-6C6
HGNC name CALR
RRID# AB_2572240
Molecular weight 48 kDa
Immunogen synthetic peptides VESGSLEDDWDFLPPKKI corresponding to amino acids 191-208 of human calreticulin, including the LC3 interacting region or LIR.
Isotype IgG1
Concentration Antibody is supplied as an aliquot of 1 mg/mL of purified antibody in 50% glycerol/PBS.
Species Reactivity Human, rat, mouse.
Applications Western blot, ICC/IF, IHC.
Suggestions for use Western blots: 1:1,000-5,000.
ICC/IF or IHC: 1:1,000-5,000.


Calreticulin was first identified as a calcium binding protein found in rabbit skeletal muscle. It appears to be a multifunctional protein found predominantly in endoplasmic reticulum (ER) and is ubiquitously expressed in a wide range of species (1). Gene knock out experiments show that the absence of the calreticulin gene is embryonically lethal (2).  One of the major functions of calreticulin appears to be buffering ER Ca2+ levels in the ER which also affects intracellular calcium signalling (3). The N-terminal region of calreticulin has a high affinity calcium binding site, whereas the C-terminal region contains multiple low affinity calcium binding sites. Calreticulin also functions as an autophagy receptor and may also act as a molecular chaperone. Calreticulin, together with its membrane anchored homolog calnexin, assists proper folding of glycoproteins, prevent protein aggregation; and manage protein quality control (4). In addition to ER, calreticulin was found to localize to intracellular, cell surface, and extracellular compartments, from which calreticulin regulates a variety of important biological processes such as cell proliferation, cell adhesion, migration and cell anoikis. Calreticulin on the cell surface may mediate phagocytosis of apoptotic or dying tumor cells by triggering immune responses and allowing the immune system to remove tumor cells. This suggests that targeting cell surface calreticulin may be a novel anti-tumor therapy (5-7).

MCA-6C6 was raised against the synthetic peptide VESGSLEDDWDFLPPKKI corresponding to amino acids 191-208 of the human calreticulin protein. This peptide includes the LC3 interacting region or LIR motif of the molecule (8). This is the region which binds LC3 and other ATG8 family molecules, and this binding is important for autophagy. The HGNC name for this protein is CALR.

References:

1. Ostwald TJ, MacLennan DH. Isolation of a high affinity calcium-binding protein from sarcoplasmic reticulum. J Biol chem.10;249(3):974-9 (1974).

2. Mesaeli N, Nakamura K, Zvaritch E, Dickie P, Dziak E, Krause, K. H, Opas M, MacLennan DH, and Michalak M. Calreticulin is essential for cardiac development. J. Cell Biol. 144, 857–868 (1999).

3. Michalak M, Groenendyk J, Szabo E, Gold LI, and Opas M. Calreticulin, a multi-process calcium-buffering chaperone of the endoplasmic reticulum. Biochem. J. 417, 651–666 (2009).

4. Bedard K, Szabo E, Michalak M, and Opas M. Cellular functions of endoplasmic reticulum chaperones calreticulin, calnexin, and ERp57. Int. Rev. Cytol. 245, 91–121 (2005).

5. Obeid M, Tesniere A, Ghiringhelli F, Fimia G M, Apetoh L, Perfettini JL, Castedo M, Mignot G, Panaretakis T, Casares N, Metivier D, Larochette N, van Endert P, Ciccosanti F, Piacentini M, Zitvogel L, and Kroemer G.  Calreticulin exposure dictates the immunogenicity of cancer cell death. Nat. Med. 13, 54–61 (2007).

6. Tesniere A, Apetoh L, Ghiringhelli F, Joza N, Panaretak T, Kepp O, Schlemmer F, Zitvogel L, and Kroemer G. Immunogenic cancer cell death: a key-lock paradigm. Curr.Opin. Immunol. 20, 504–511 (2008).

7. Gardai SJ, McPhillips KA, Frasch SC, Janssen WJ, Starefeldt A, Murphy-Ullrich JE, Bratton DL, Oldenborg PA, Michalak M, and Henson PM. Cell-surface calreticulin initiates clearance of viable or apoptotic cells through trans-activation of LRP on the phagocyte. Cell 123, 321–334 (2005).

8. Birgisdottir AB, Lamark T and Johansen T. The LIR motif – crucial for selective autophagy. J. Cell Sci. 126, 3237–3247 (2013).

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