Co-ordinated activation of classical and novel PKC isoforms is required for PMA-induced mTORC1 activation

PLoS One. 2017 Sep 19;12(9):e0184818. doi: 10.1371/journal.pone.0184818. eCollection 2017.

Abstract

Protein kinase C (PKC) has been shown to activate the mammalian target of rapamycin complex 1 (mTORC1) signaling pathway, a central hub in the regulation of cell metabolism, growth and proliferation. However, the mechanisms by which PKCs activate mTORC1 are still ambiguous. Our previous study revealed that activation of classical PKCs (cPKC) results in the perinuclear accumulation of cPKC and phospholipase D2 (PLD2) in recycling endosomes in a PLD2-dependent manner. Here, we report that mTORC1 activation by phorbol 12,13-myristate acetate (PMA) requires both classic, cPKC, and novel PKC (nPKC) isoforms, specifically PKCη, acting through distinct pathways. The translocation of mTOR to perinuclear lysosomes was detected after treatment of PKC activators, which was not colocalized with PKCα- or RAB11-positive endosomes and was not inhibited by PLD inhibitors. We found that PKCη inhibition by siRNA or bisindolylmaleimide I effectively decreased mTOR accumulation in lysosomes and its activity. Also, we identified that PKCη plays a role upstream of the v-ATPase/Ragulator/Rag pathway in response to PMA. These data provides a spatial aspect to the regulation of mTORC1 by sustained activation of PKC, requiring co-ordinated activation of two distinct elements, the perinuclear accumulation of cPKC- and PLD-containing endosomes and the nPKC-dependent translation of of mTOR in the perinuclear lysosomes. The close proximity of these two distinct compartments shown in this study suggests the possibility that transcompartment signaling may be a factor in the regulation of mTORC1 activity and also underscores the importance of PKCη as a potential therapeutic target of mTORC-related disorders.

MeSH terms

  • Adenosine Triphosphatases / metabolism
  • Carbazoles / pharmacology
  • Endocytosis / drug effects
  • Endosomes / metabolism
  • Enzyme Activation / drug effects
  • HEK293 Cells
  • HeLa Cells
  • Humans
  • Lysosomes / metabolism
  • Mechanistic Target of Rapamycin Complex 1
  • Multiprotein Complexes / metabolism*
  • Phospholipase D / metabolism
  • Phosphorylation / drug effects
  • Protein Isoforms / antagonists & inhibitors
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism*
  • RNA Interference
  • Signal Transduction / drug effects
  • TOR Serine-Threonine Kinases / metabolism*
  • Tetradecanoylphorbol Acetate / pharmacology*

Substances

  • Carbazoles
  • Multiprotein Complexes
  • Protein Isoforms
  • Go 6976
  • protein kinase C eta
  • Mechanistic Target of Rapamycin Complex 1
  • TOR Serine-Threonine Kinases
  • Protein Kinase C
  • phospholipase D2
  • Phospholipase D
  • Adenosine Triphosphatases
  • Tetradecanoylphorbol Acetate