PKCδ phosphorylation is an upstream event of GSK3 inactivation-mediated ROS generation in TGF-β1-induced senescence

Abstract

Transforming growth factor β1 (TGF-β1) induces Mv1Lu cell senescence through inactivating glycogen synthase kinase 3 (GSK3), thereby inactivating complex IV and increasing intracellular ROS. In the present study, we identified protein kinase C delta (PKCδ) as an upstream regulator of GSK3 inactivation in this mechanism of TGF-β1-induced senescence. When Mv1Lu cells were exposed to TGF-β1, PKCδ phosphorylation simultaneously increased with GSK3 phosphorylation, and then AKT and ERK were phosphorylated. AKT phosphorylation and Smad signaling were independent of GSK3 phosphorylation, but ERK phosphorylation was downstream of GSK3 inactivation. TGF-β1-triggered GSK3 phosphorylation was blocked by inhibition of PKCδ, using its pharmacological inhibitor, Rottlerin, or overexpression of a dominant negative PKCδ mutant, but GSK3 inhibition with SB415286 did not alter PKCδ phosphorylation. Activation of PKCδ by PMA delayed cell growth and increased intracellular ROS level, but did not induce senescent phenotypes. In addition, overexpression of wild type or a constitutively active PKCδ mutant was enough to delay cell growth and decrease the mitochondrial oxygen consumption rate and complex IV activity, but weakly induce senescence. However, PMA treatment on Mv1Lu cells, which overexpress wild type and constitutively active PKCδ mutants, effectively induced senescence. These results indicate that PKCδ plays a key role in TGF-β1-induced senescence of Mv1Lu cells through the phosphorylation of GSK3, thereby triggering mitochondrial complex IV dysfunction and intracellular ROS generation.

Rottlerin, a natural polyphenol compound, inhibits upregulation of matrix metalloproteinase-9 and brain astrocytic migration by reducing PKC-δ-dependent ROS signal

“…Herein, we are the first group to establish that rottlerin reduce Nox/ROS signal induced by PMA in brain astrocytes. The finding is consistent with previous study indicated that PKCδ phosphorylation is an upstream event of GSK3 inactivation-mediated ROS generation in TGF-β1induced senescence [43]. It is consistent with previous report indicated that rottlerin induces cyclooxygenase-2 upregulation through reactive oxygen speciesindependent pathway in HEI-OC1 cells [44].…”

Berberine Inhibits Oxygen Consumption Rate Independent of Alteration in Cardiolipin Levels in H9c2 Cells

“…More recently, we demonstrated that BBR reduced DAG levels in palmitate-treated insulin resistant H9c2 cells [9]. Overexpression of wild type or a constitutively active PKCδ mutant was shown to decrease mitochondrial oxygen consumption in Mv1Lu cells [18]. In the current study, BBR treatment of H9c2 cells attenuated the palmitate-mediated increase in membrane-associated PKCδ yet still resulted in a reduction in OCR.…”

Metabolic features and regulation in cell senescence

“…Iron chelation using deferoxamine (DFO) decreased complex II activity via down-regulated translation of the complex II iron-sulfur subunit, prior to increasing p27 kip1 -mediated cell cycle arrest, and eventual induction of senescence in Chang normal liver cells (21, 22). Transforming growth factor β1 (TGF β1) triggered senescence of Mv1Lu lung epithelial cells by inhibiting complex IV activity via the PKCδ/GSK3 axis, and increasing ROS (23–25). Ionizing radiation induced endothelial cell senescence through a mitochondrial respiratory complex II defect and superoxide generation (26).…”