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Calpain‐2 Activates Akt via TGFβ1‐mTORC2 Pathway in Pulmonary Artery Smooth Muscle Cells
Author(s) -
Abeyrathna Prasanna Kumara,
Kovacs Laszlo,
Su Yunchao
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.719.8
Subject(s) - protein kinase b , platelet derived growth factor receptor , microbiology and biotechnology , phosphorylation , mtorc2 , calpain , chemistry , cancer research , biology , biochemistry , growth factor , mtorc1 , receptor , enzyme
Calpain, a calcium‐dependent nonlysosomal neutral cysteine endopeptidase, activates an intracrine TGFβ pathway in pulmonary artery smooth muscle cells (PASMCs) and plays an important role in smooth muscle cell hyperproliferation and collagen synthesis in pulmonary vascular remodeling of pulmonary arterial hypertension (PAH). Akt is a serine‐threonine kinase involved in many cellular processes including cell proliferation and collagen synthesis. In this study, we investigated the connection between calpain activation and Akt in the collagen synthesis and cell proliferation of PASMCs caused by PDGF. We found that inhibition of calpain‐2 by calpain inhibitor, MDL28170 and calpain‐2 siRNA attenuated Akt phosphorylation at serine‐473 (S473) and threonine‐308 (T308) as well as collagen synthesis and cell proliferation of PASMCs induced by PDGF. Overexpression of calpain‐2 in PASMCs induced dramatic increases in Akt phosphorylation at S473 and T308. The cell‐permeable specific TGFβ receptor inhibitor SB431542 attenuated Akt phosphorylation at both S473 and T308 induced by PDGF and by overexpressed calpain‐2 in PASMCs. Moreover, SB‐431452 and knocking down ALK5 significantly reduced PDGF‐induced collagen synthesis and cell proliferation of PASMCs. Nevertheless, neutralizing extracellular TGFβ1 using a cell‐impermeable TGFβ1 neutralizing antibody did not affect PDGF‐induced Akt phosphorylation at S473 and T308. Further, inhibition of mTORC2 by knocking down its component protein Rictor prevented PDGF‐induced Akt phosphorylation at S473 and T308. Additionally, calpain inhibitor MDL28170 inhibited PDGF‐induced increase in mTORC2 activity. These data provide first evidence supporting that calpain‐2 up‐regulates PDGF‐induced Akt phosphorylation via an intracrine TGFβ1/mTORC2 mechanism. Support or Funding Information Supported by NIH, FAMRI and Department of Veterans Affairs