Abstract 14947: Upregulation of Drp1 Receptor Proteins MiD49 and MiD51 by miR-34a-3p Increases Mitochondrial Fission and Cell Proliferation in Pulmonary Arterial Hypertension: Therapeutic Implications
Introduction: The obstructive vasculopathy in pulmonary arterial hypertension (PAH) is characterized by hyperproliferation and apoptosis-resistance of pulmonary artery smooth muscle cells (PASMC). This cancer-like phenotype is due in part, to excessive mitochondrial fission caused by activation of dynamin related protein-1 (Drp1). Drp1 must bind adapter proteins in the outer mitochondrial membrane to create the fission apparatus. Here we examine the role of two newly discovered Drp1 binding proteins, mitochondrial dynamics protein of 49 and 51 kDa (MiD49 and MiD51) in PAH.
Hypothesis: Upregulation of MiD49 and MiD51 increase mitochondrial fission and cell proliferation in human and experimental PAH.
Methods: Immunoblots of PASMC and histology of lung sections were used to assess MiD49 and MiD51 expression in control (n=3) vs. PAH patients (n=6). PAH was induced in rats by injection of monocrotaline (MCT). The effects of manipulating MiDs on cell proliferation, cell cycle, and apoptosis were assessed in PAH versus control PASMC using flow cytometry and an ELISA assay, respectively. The mitochondrial network was studied using confocal imaging. MicroRNAs (miR) regulating MiD expressions were identified using in silico analyses, microarray and qRT-PCR.
Results: Mitochondria are fragmented and MiDs are upregulated in human and MCT induced PAH PASMC. siRNA against MiD49 and MiD51 increased mitochondrial fusion and reduced proliferation by arresting PAH PASMC in the G1/G0 phase. Overexpressing MiD49 or 51 increased proliferation in normal PASMC. siMiD51 induced apoptosis in PAH PASMC. Silencing the other Drp1 receptors, Mff or Fis1, did not inhibit cell proliferation. In silico analysis identified miR-34a-3p as a putative negative regulator of MiDs. miR-34a-3p is decreased in PAH and anti-miR-34a-3p increased MiD expressions in normal PASMC, recapitulating the PAH phenotype.
Conclusion: MiD49 and MiD51 are upregulated in PAH and promote mitochondrial fission and cell proliferation in PAH PASMC. Decreased miR-34a-3p expression underlies upregulation of MiDs in PAH. Silencing MiDs enhance mitochondrial fusion and reduce cell proliferation in PAH. Inhibiting MiDs, or restoring expression of miR-34a-3p, may have therapeutic benefit in PAH.
Author Disclosures: A. Dasgupta: None. K. Chen: None. J. Fu: None. J. Mewburn: None. S.L. Archer: None.
- © 2016 by American Heart Association, Inc.