TRPC3 shapes the ER-mitochondria Ca2+ transfer characterizing tumour-promoting senescence

Abstract

Cellular senescence is implicated in a great number of diseases including cancer. Although alterations in mitochondrial metabolism were reported as senescence drivers, the underlying mechanisms remain elusive. We report the mechanism altering mitochondrial function and OXPHOS in stress-induced senescent fibroblasts. We demonstrate that TRPC3 protein, acting as a controller of mitochondrial Ca2+ load via negative regulation of IP3 receptor-mediated Ca2+ release, is down regulated in senescence regardless of the type of senescence inducer. This remodelling promotes cytosolic/mitochondrial Ca2+ oscillations and elevates mitochondrial Ca2+ load, mitochondrial oxygen consumption rate and oxidative phosphorylation. Re-expression of TRPC3 in senescent cells diminishes mitochondrial Ca2+ load and promotes escape from OIS-induced senescence. Cellular senescence evoked by TRPC3 downregulation in stromal cells displays a proinflammatory and tumour-promoting secretome that encourages cancer epithelial cell proliferation and tumour growth in vivo. Altogether, our results unravel the mechanism contributing to pro-tumour behaviour of senescent cells.

Expression of the Calcium-Binding Protein CALB1 Is Induced and Controls Intracellular Ca2+ Levels in Senescent Cells

“…Together with other works which reported increased Ca 2+ levels in several senescence contexts [ 5 , 8 , 9 , 10 , 11 ], our observations suggest that a rise in intracellular Ca 2+ contents could be a new hallmark of cellular senescence. Although some contributions of Ca 2+ in senescence have already been identified, its precise role in this context is not fully understood yet [ 5 , 8 , 9 , 10 , 11 ]. In our study, we observed an increase in Ca 2+ contents both in the cytosol and in intracellular stocks, which are mainly in the ER and in the mitochondria.…”

“…Finally, as an increase in intracellular Ca 2+ contents appears to be a common mark of senescence based on our data in epithelial cells ( Figure 1 ) and on data in other cell types according to previous reports [ 6 , 7 , 11 ], we investigated whether induction of the expression of calcium-buffering calbindin-type proteins could also be a common mark of senescent cells. In addition to Raf and Mek oncogenes, bleomycin, and nutlin ( Figure 1 ), other senescence inducers such as Ras oncogene activation, H 2 O 2 , TGFβ, or KCl, which are all known to induce senescence in HMECT [ 14 , 19 , 20 , 21 ], also triggered a rise in CALB1 expression in HMECT ( Figure 5 A).…”

“…Regulation of intracellular Ca 2+ levels has been recently reported in some contexts of cellular senescence, and we and others have demonstrated that Ca 2+ transfer from endoplasmic reticulum to mitochondria promotes cellular senescence [ 8 , 9 , 10 , 11 ]. To know whether Ca 2+ level alterations are a classical mark of senescent cells, we measured Ca 2+ levels in HMEC in proliferation versus senescence using different types of senescence inducers: oncogenes, the chemotherapeutic agent bleomycin, or the p53 stabilizer nutlin-3.…”

“…Decreased expression of transient receptor potential cation channel subfamily C member 3 (TRPC3) was observed in response to many senescence inducers. TRPC3 re-expression promotes escape from oncogene-induced senescence by decreasing mitochondrial Ca 2+ load by inhibiting ITPR3 activity [ 11 ]. Beyond these channels, cells also have a calcium-buffering system that shapes intracellular Ca 2+ signals.…”

From the divergence of senescent cell fates to mechanisms and selectivity of senolytic drugs

“…Mitochondrial mass increases in senescence, but this is accompanied by mitochondrial dysfunction and the production of ROS, generating chronic oxidative stress [125,126]. ER-mitochondria contact sites appear critical in senescence regulation [127], and mitochondrial dysfunction and ROS production were shown to be mediated in many senescence models by increased IP3R-mediated mitochondrial calcium uptake from the ER following ITPR downregulation [128]. Oxidative stress induces senescence in many settings [129,130], but the upregulation of ROS detoxifying systems is also critical for the decision to undergo senescence over apoptosis [126].…”