Author:

Keywords:

Science & Technology, Life Sciences & Biomedicine, Biochemistry & Molecular Biology, Cell Biology, Mitochondria, Calcium, Sphingosine kinase, Sphingosine 1-phosphate, Mitofusin-2, Endoplasmic reticulum, MITOFUSIN 2, ESSENTIAL COMPONENT, CALCIUM, PROTEIN, 1-PHOSPHATE, MEMBRANE, DEFICIENCY, METABOLISM, CONTACT, CALPAIN, Sphingosine kinase 1, Cell Movement, Cell Proliferation, Endoplasmic Reticulum, GTP Phosphohydrolases, HeLa Cells, Humans, Lysophospholipids, Mitochondrial Proteins, Phosphotransferases (Alcohol Group Acceptor), Signal Transduction, Sphingosine, Sphingosine-1-Phosphate Receptors, Hela Cells, DYSFUNCTION, 0601 Biochemistry and Cell Biology, 1108 Medical Microbiology, 3101 Biochemistry and cell biology

Abstract:

Sphingosine kinase 1 (SK1) converts sphingosine to the bioactive lipid sphingosine 1-phosphate (S1P). S1P binds to G-protein-coupled receptors (S1PR1-5) to regulate cellular events, including Ca2+ signaling. The SK1/S1P axis and Ca2+ signaling both play important roles in health and disease. In this respect, Ca2+ microdomains at the mitochondria-associated endoplasmic reticulum (ER) membranes (MAMs) are of importance in oncogenesis. Mitofusin 2 (MFN2) modulates ER-mitochondria contacts, and dysregulation of MFN2 is associated with malignancies. We show that overexpression of SK1 augments agonist-induced Ca2+ release from the ER resulting in increased mitochondrial matrix Ca2+. Also, overexpression of SK1 induces MFN2 fragmentation, likely through increased calpain activity. Further, expressing putative calpain-cleaved MFN2 N- and C-terminal fragments increases mitochondrial matrix Ca2+ during agonist stimulation, mimicking the SK1 overexpression in cells. Moreover, SK1 overexpression enhances cellular respiration and cell migration. Thus, SK1 regulates MFN2 fragmentation resulting in increased mitochondrial Ca2+ and downstream cellular effects.