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Calreticulin – a multifaced protein

Zuzanna Kanduła
Zuzanna Kanduła
 and 
Krzysztof Lewandowski
Krzysztof Lewandowski
   | May 18, 2021
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Article Category: Review
Published Online: May 18, 2021
Page range: 328 - 336
Received: Jul 02, 2020
Accepted: Nov 24, 2020
DOI: https://doi.org/10.5604/01.3001.0014.8892
Keywords
© 2021 Zuzanna Kanduła et al., published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

Fig. 1

Linear representation of human wild type (A) and mutant type 1 and 2 (B) calreticulin domains
Linear representation of human wild type (A) and mutant type 1 and 2 (B) calreticulin domains

Fig. 1

The function of calreticulin (CALR) in normal and stress conditions, and the mechanism of mutant CALR (CALR MUT) interaction with the MPL protein in the secretion pathway leading to neoplastic transformation of hematopoietic stem cell. A. In normal conditions, CALR participates in various processes in the cells, including glycoprotein chaperoning, the regulation of Ca2+ homeostasis, antigen processing and presentation for adaptive immune response. Wild type CALR presents acidic pH values (preserved KDEL retention signal), in contrast to CALR-s mutant protein. Normal cells express low amounts of the CALR ’eat-me‘ signal, and high amounts of the integrin associated protein (IAP, CD47) ’don’t eat-me‘ signal on the surface. B. In stress conditions, upon the induction of apoptosis, phosphatidylserine (PS) and CALR are translocated to the outer leaflet of the cell membrane. Some proapoptotic stimuli (i.e. UVB irradiation) may initiate the mobilization of CALR to the outer cell membrane even before the PS translocation. CALR molecules on the surface of apoptotic cells are able to trans-activate low density lipoprotein receptor-related protein 1 (LRP1, CD91) on the phagocytes surface, promoting phagocytosis of apoptotic cells. C. In normal conditions, the P-domain of CALR cannot interact with the MPL receptor (the inhibitory function of the P-domain). The inhibitory effect of the P-domain is abolished by the novel C-terminus in KDEL-deleted CALR. In the case of CALR MUT, after synthesis, abnormal protein is moved through the ER to bind to immature MPL. Thereafter, the CALR MUT-MPL complex is stabilized and translocated to the cell surface in the pre-activated form which results in the induction of signalling via the JAK-STAT pathway; CALR WT – wild type calreticulin, KDEL – endoplasmic reticulum retention signal, --- – negatively charged isoelectric points, CALR MUT – mutant calreticulin, +++ positively charged isoelectric points, MPL – thrombopoietin receptor, CD47 – integrin associated protein (IAP), PS – phosphatidylserine, TPO – thrombopoietin
The function of calreticulin (CALR) in normal and stress conditions, and the mechanism of mutant CALR (CALR MUT) interaction with the MPL protein in the secretion pathway leading to neoplastic transformation of hematopoietic stem cell. A. In normal conditions, CALR participates in various processes in the cells, including glycoprotein chaperoning, the regulation of Ca2+ homeostasis, antigen processing and presentation for adaptive immune response. Wild type CALR presents acidic pH values (preserved KDEL retention signal), in contrast to CALR-s mutant protein. Normal cells express low amounts of the CALR ’eat-me‘ signal, and high amounts of the integrin associated protein (IAP, CD47) ’don’t eat-me‘ signal on the surface. B. In stress conditions, upon the induction of apoptosis, phosphatidylserine (PS) and CALR are translocated to the outer leaflet of the cell membrane. Some proapoptotic stimuli (i.e. UVB irradiation) may initiate the mobilization of CALR to the outer cell membrane even before the PS translocation. CALR molecules on the surface of apoptotic cells are able to trans-activate low density lipoprotein receptor-related protein 1 (LRP1, CD91) on the phagocytes surface, promoting phagocytosis of apoptotic cells. C. In normal conditions, the P-domain of CALR cannot interact with the MPL receptor (the inhibitory function of the P-domain). The inhibitory effect of the P-domain is abolished by the novel C-terminus in KDEL-deleted CALR. In the case of CALR MUT, after synthesis, abnormal protein is moved through the ER to bind to immature MPL. Thereafter, the CALR MUT-MPL complex is stabilized and translocated to the cell surface in the pre-activated form which results in the induction of signalling via the JAK-STAT pathway; CALR WT – wild type calreticulin, KDEL – endoplasmic reticulum retention signal, --- – negatively charged isoelectric points, CALR MUT – mutant calreticulin, +++ positively charged isoelectric points, MPL – thrombopoietin receptor, CD47 – integrin associated protein (IAP), PS – phosphatidylserine, TPO – thrombopoietin
eISSN:
1732-2693
Language:
English
Publication timeframe:
Volume Open
Journal Subjects:
Life Sciences, Molecular Biology, Microbiology and Virology, Medicine, Basic Medical Science, Immunology
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