SIRT3 Deacetylates Ceramide Synthases

Abstract

Experimental evidence supports the role of mitochondrial ceramide accumulation as a cause of mitochondrial dysfunction and brain injury after stroke. Herein, we report that SIRT3 regulates mitochondrial ceramide biosynthesis via deacetylation of ceramide synthase (CerS) 1, 2, and 6. Reciprocal immunoprecipitation experiments revealed that CerS1, CerS2, and CerS6, but not CerS4, are associated with SIRT3 in cerebral mitochondria. Furthermore, CerS1, -2, and -6 are hyperacetylated in the mitochondria of SIRT3-null mice, and SIRT3 directly deacetylates the ceramide synthases in a NAD ؉ -dependent manner that increases enzyme activity. Investigation of the SIRT3 role in mitochondrial response to brain ischemia/reperfusion (IR) showed that SIRT3-mediated deacetylation of ceramide synthases increased enzyme activity and ceramide accumulation after IR. Functional studies demonstrated that absence of SIRT3 rescued the IR-induced blockade of the electron transport chain at the level of complex III, attenuated mitochondrial outer membrane permeabilization, and decreased reactive oxygen species generation and protein carbonyls in mitochondria. Importantly, Sirt3 gene ablation reduced the brain injury after IR. These data support the hypothesis that IR triggers SIRT3-dependent deacetylation of ceramide synthases and the elevation of ceramide, which could inhibit complex III, leading to increased reactive oxygen species generation and brain injury. The results of these studies highlight a novel mechanism of SIRT3 involvement in modulating mitochondrial ceramide biosynthesis and suggest an important role of SIRT3 in mitochondrial dysfunction and brain injury after experimental stroke.

The Cross-Talk Between Sphingolipids and Insulin-Like Growth Factor Signaling: Significance for Aging and Neurodegeneration

“…The presence of six tightly regulated and interdependent ceramide synthases plus their splice variants assures the necessary variation in synthesized ceramides [ 30 ]. CerSs are known to undergo phosphorylation, acetylation, N -glycosylation, and ubiquitination, implying tight (but still poorly understood) regulation [ 30 , 31 ].

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Ceramide synthase-6 confers resistance to chemotherapy by binding to CD95/Fas in T-cell acute lymphoblastic leukemia

“…Binding of CERS6 to Fas persisted with C199V mutation, suggesting that C199 is not critical for CERS6 binding. BCL2L13 and SIRT3 are two proteins reported to be interacting with CERS6, where the former is shown to inhibit the activity of CERS6 44 , while the latter deacetylates CERS6 to cause an increase in its activity 45 . These interactions affect the activity of CERS6, but there are no reports showing that CERS6 affects the function of other proteins.…”

Sirtuins, Mitochondria and the Melatonergic Pathway in Alzheimer&rsquo;s Disease<strong> </strong>

“…Clearly, the role of sirtuins in modulating gut microbiome-derived butyrate will modulate ceramide levels and effects in AD. This requires future investigation as some data indicates that under conditions of ischaemia-reperfusion, SIRT3 deacetylates ceramide synthase, leading to an increase in ceramide synthesis [92]. The interactions of the sirtuins with the regulation of ceramide at different sites will be important to determine…”

“…As noted, ceramide is damaging to mitochondria via a number of mechanisms, including decreasing mitochondrial Complex III, PDC and OXPHOS [92]. Recent work shows all factors and enzymes of the melatonergic pathway to be expressed in mitochondria [64], including AANAT, acetylserotonin methyltransferase (ASMT), 14-3-3 and acetyl-CoA, reviewed in [8].…”

“…Increased ceramide seems to contribute to AD pathophysiology. However, under conditions of ischaemia-reperfusion, SIRT3 deacetylates ceramide synthase, leading to an increase in ceramide synthesis [92]. Clarification as to the interactions of the sirtuins with circadian rhythm of ceramide synthesis is required, including the impact of different sirtuins on the ceramide/sphingosine-1phosphate ratio [81].…”