Studies have shown that mutant calreticulin (CALR) constitutively activates the thrombopoietin (TPO) receptor MPL and thus plays a causal role in the development of myeloproliferative neoplasms (MPNs). To further elucidate the molecular mechanism by which mutant CALR promotes MPN development, we studied the subcellular localization of mutant CALR and its importance for the oncogenic properties of mutant CALR. Here, mutant CALR accumulated in the Golgi apparatus, and its entrance into the secretion pathway and capacity to interact with N-glycan were required for its oncogenic capacity via the constitutive activation of MPL. Mutant CALR-dependent MPL activation was resistant to blockade of intracellular protein trafficking, suggesting that MPL is activated before reaching the cell surface. However, removal of MPL from the cell surface with trypsin shut down downstream activation, implying that the surface localization of MPL is required for mutant CALR-dependent activation. Furthermore, we found that mutant CALR and MPL interact on the cell surface. Based on these findings, we propose a model in which mutant CALR induces MPL activation on the cell surface to promote MPN development.
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Mutant Calreticulin in MPN: Mechanistic Insights and Therapeutic Implications.
Curr Hematol Malig Rep
January 2025
Division of Hematology, Department of Medicine, Stanford University School of Medicine, Stanford, CA, 94305, USA.
Purpose Of Review: More than a decade following the discovery of Calreticulin (CALR) mutations as drivers of myeloproliferative neoplasms (MPN), advances in the understanding of CALR-mutant MPN continue to emerge. Here, we summarize recent advances in mehanistic understanding and in targeted therapies for CALR-mutant MPN.
Recent Findings: Structural insights revealed that the mutant CALR-MPL complex is a tetramer and the mutant CALR C-terminus is exposed on the cell surface.
CALR frameshift mutation detection in myeloproliferative neoplasms by microfluidic chip analysis.
Lab Med
December 2024
Department of Pathology and Genomic Medicine, Houston Methodist Hospital, Houston, TX, United States.
Background: CALR mutation analysis is routinely used to diagnose BCR/ABL1-negative myeloproliferative neoplasms. The 2 most common CALR mutations are a 52-base pair (bp) deletion and a 5-bp insertion, which account for approximately 85% of cases.
Methods: To evaluate our new microfluidic chip assay, we tested CALR mutant and wild-type specimens that were previously analyzed using conventional methods at a reference laboratory.
The aberrantly activated AURKB supports and complements the function of AURKA in CALR mutated cells through regulating the cell growth and differentiation.
Exp Cell Res
January 2025
Department of Hematology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, China; Blood Diseases Institute, Xuzhou Medical University, Xuzhou, China. Electronic address:
Aurora kinase B (AURKB) was reported to assist Aurora kinase A (AURKA) to regulate cellular mitosis. AURKA has been found activated in myeloproliferative neoplasms (MPNs) patients with CALR gene mutation, however, it's unclear whether AURKB displays a compensatory function of AURKA in regulation of CALR mutant cell growth and differentiation. Here, we found that AURKB, similar with AURKA, was aberrantly activated in CALR mutant patients, and displayed a more tolerance to the aurora kinase inhibitor.
View Article and Find Full Text PDFMolecular Profile of BCR-ABL1 Negative Myeloproliferative Neoplasm in a Moroccan Population.
Asian Pac J Cancer Prev
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Cytogenetics Laboratory, Pasteur Institute of Morocco (IPM), 1 Place Louis Pasteur, 20360 Casablanca, Morocco.
Introduction: Myeloproliferative neoplasms (MPN) are associated with clonal hematopoiesis, genomic instability, hemostasis dysregulation, and immune response. Classic BCR-ABL1 negative myeloproliferative neoplasms (BCR-ABL1 negative MPN), including polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are frequently associated with somatic abnormalities in JAK2, CALR, and MPL. Mutant clones induce an inflammatory immune response leading to immuno-thrombosis.
View Article and Find Full Text PDFMyeloproliferative Neoplasm-like Mutations of Calreticulin Induce Phenotypes Associated with Calreticulin Dysfunction in .
Int J Mol Sci
October 2024
Department of Biochemistry and Genetics, School of Sciences, University of Navarra, 31008 Pamplona, Spain.
In previous research, we created a model with homozygous mutations in calreticulin similar to those found in patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF), two myeloproliferative neoplasms (MPNs). This model, lacking JAK orthologs, enabled us to examine the transcriptomic effects caused by mutant calreticulin without the influence of JAK/STAT activation, the primary pathogenic mechanism associated with calreticulin mutations known to date. Most of the gene expression changes observed seemed to be due to a partial loss of protein function, with the alteration of the extracellular matrix being particularly notable.
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