Novel molecular mechanism of cellular transformation by a mutant molecular chaperone in myeloproliferative neoplasms

• Published in: Cancer science Vol. 108; no. 10; pp. 1907 - 1912
• Main Authors: Araki, Marito, Komatsu, Norio
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.10.2017; John Wiley and Sons Inc
• Subjects: Amino acids; Autocrine; Autocrine Communication; Autocrine signalling; Binding Sites; Calreticulin; Calreticulin - chemistry; Calreticulin - genetics; Calreticulin - metabolism; Cell surface; Cell Transformation, Neoplastic - genetics; Cell Transformation, Neoplastic - metabolism; Cytokines; Endoplasmic reticulum; Frameshift Mutation; Gene Expression Regulation, Neoplastic; Genes; Genetic transformation; Humans; JAK2; Kinases; Leukemia; Mutation; Myeloproliferative Disorders - genetics; Myeloproliferative Disorders - metabolism; myeloproliferative neoplasm; Peptides; Protein Binding; Protein Conformation; Proteins; Receptors, Thrombopoietin - metabolism; Retention; Review; Signal Transduction; Solicited Review; Thrombopoietin; thrombopoietin receptor; Tumorigenesis; Tumors; Japan; thrombopoietin receptor; calreticulin; Autocrine; JAK2; myeloproliferative neoplasm
• ISSN: 1347-9032; 1349-7006
• DOI: 10.1111/cas.13327

Deregulation of the cytokine‐receptor signaling pathway plays a significant role in tumorigenesis. Such deregulation is frequently caused by alterations in the genes involved in the signaling pathway. At the end of 2013, recurrent somatic mutations in the calreticulin (CALR) gene that encodes a molecular chaperone were identified in a subset of patients with Philadelphia‐chromosome negative myeloproliferative neoplasms (MPN). The present review focuses on the role of CALR mutations in the oncogenic transformations observed in MPN. All the CALR mutations were found to generate a + 1 frameshift in the reading frame on exon 9, which encodes the carboxy (C)‐terminus end of CALR, and thus conferred a common mutant‐specific sequence in all the CALR mutants. The mutant CALR (but not the wild‐type) constitutively activates the thrombopoietin (TPO) receptor, myeloproliferative leukemia protein (MPL), even in the absence of TPO to induce cellular transformation. Preferential interaction between the mutant CALR and MPL is achieved by a presumptive conformational change induced by the mutant‐specific C‐terminus domain, which allows N‐domain binding to MPL. Even though mutant CALR is expressed on the cell surface and is secreted out of cells, it only presents autocrine capacity for MPL activation. These findings define a novel molecular mechanism by which the mutant molecular chaperone constitutively activates the cytokine receptor to induce cellular transformation. This review covered a novel molecular mechanism by which the mutant molecular chaperone constitutively activates the cytokine receptor to induce cellular transformation.