Defective interaction of mutant calreticulin and SOCE in megakaryocytes from patients with myeloproliferative neoplasms.

Abstract

Approximately one-fourth of patients with essential thrombocythemia or primary myelofibrosis carry a somatic mutation of the calreticulin gene (CALR), the gene encoding for calreticulin. A 52-bp deletion (type I mutation) and a 5-bp insertion (type II mutation) are the most frequent genetic lesions. The mechanism(s) by which a CALR mutation leads to a myeloproliferative phenotype has been clarified only in part. We studied the interaction between calreticulin and store-operated calcium (Ca2+) entry (SOCE) machinery in megakaryocytes (Mks) from healthy individuals and from patients with CALR-mutated myeloproliferative neoplasms (MPNs). In Mks from healthy subjects, binding of recombinant human thrombopoietin to c-Mpl induced the activation of signal transducer and activator of transcription 5, AKT, and extracellular signal-regulated kinase 1/2, determining inositol triphosphate-dependent Ca2+ release from the endoplasmic reticulum (ER). This resulted in the dissociation of the ER protein 57 (ERp57)-mediated complex between calreticulin and stromal interaction molecule 1 (STIM1), a protein of the SOCE machinery that leads to Ca2+ mobilization. In Mks from patients with CALR-mutated MPNs, defective interactions between mutant calreticulin, ERp57, and STIM1 activated SOCE and generated spontaneous cytosolic Ca2+ flows. In turn, this resulted in abnormal Mk proliferation that was reverted using a specific SOCE inhibitor. In summary, the abnormal SOCE regulation of Ca2+ flows in Mks contributes to the pathophysiology of CALR-mutated MPNs. In perspective, SOCE may represent a new therapeutic target to counteract Mk proliferation and its clinical consequences in MPNs.

• Authors: Christian A Di Buduo, Vittorio Abbonante, Caroline Marty, Francesco Moccia, Elisa Rumi, Daniela Pietra, Paolo M Soprano, Dmitry Lim, Daniele Cattaneo, Alessandra Iurlo, Umberto Gianelli, Giovanni Barosi, Vittorio Rosti, Isabelle Plo, Mario Cazzola, Alessandra Balduini
• Journal: Blood (Blood) Vol. 135 Issue 2 Pg. 133-144 (01 09 2020) ISSN: 1528-0020 [Electronic] United States
• PMID: 31697806 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
• Copyright: © 2020 by The American Society of Hematology.

Chemical References

• CALR protein, human
• Calcium Release Activated Calcium Channels
• Calreticulin
• Neoplasm Proteins
• STIM1 protein, human
• Stromal Interaction Molecule 1
• Protein Disulfide-Isomerases
• PDIA3 protein, human

Topics

• Calcium Release Activated Calcium Channels (genetics, metabolism)
• Calreticulin (genetics, metabolism)
• Case-Control Studies
• Humans
• Megakaryocytes (metabolism, pathology)
• Mutation
• Myeloproliferative Disorders (genetics, metabolism, pathology)
• Neoplasm Proteins (genetics, metabolism)
• Protein Disulfide-Isomerases (genetics, metabolism)
• Stromal Interaction Molecule 1 (genetics, metabolism)