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

• Published in: Blood Vol. 135; no. 2; pp. 133 - 144
• Main Authors: Di Buduo, Christian A., Abbonante, Vittorio, Marty, Caroline, Moccia, Francesco, Rumi, Elisa, Pietra, Daniela, Soprano, Paolo M., Lim, Dmitry, Cattaneo, Daniele, Iurlo, Alessandra, Gianelli, Umberto, Barosi, Giovanni, Rosti, Vittorio, Plo, Isabelle, Cazzola, Mario, Balduini, Alessandra
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 09.01.2020; American Society of Hematology
• Subjects: Calcium Release Activated Calcium Channels - genetics; Calcium Release Activated Calcium Channels - metabolism; Calreticulin - genetics; Calreticulin - metabolism; Case-Control Studies; Humans; Life Sciences; Megakaryocytes - metabolism; Megakaryocytes - pathology; Mutation; Myeloid Neoplasia; Myeloproliferative Disorders - genetics; Myeloproliferative Disorders - metabolism; Myeloproliferative Disorders - pathology; Neoplasm Proteins - genetics; Neoplasm Proteins - metabolism; Protein Disulfide-Isomerases - genetics; Protein Disulfide-Isomerases - metabolism; Stromal Interaction Molecule 1 - genetics; Stromal Interaction Molecule 1 - metabolism
• ISSN: 0006-4971; 1528-0020; 1528-0020
• DOI: 10.1182/blood.2019001103

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. •In normal Mks, calreticulin regulates the activation of SOCE by interacting with ERp57 and STIM1.•In CALR-mutated MPNs, defective interaction between mutant calreticulin and SOCE proteins promotes Mk proliferation. [Display omitted]