Effects of cations on ceramide-activated protein phosphatase 2A

Abstract

Characterization of ceramide-effector(s), which includes protein phosphatase 2A (PP2A) is an important prelude to understanding the molecular basis of sphingolipid-mediated biological effects such as cell growth, differentiation and apoptosis. Recently, the existence of a metal-dependent form of PP2A has been reported (Cai et al., 1995). In this study, we investigated the effects of metal ions and chelators on ceramide-activated PP2A (CAPP). Our study demonstrates that at 0.5 mM concentration, Mg 2+ appears to have no significant effect on either basal or ceramide-stimulated phosphatase activities, whereas Ca 2+ stimulated the basal phosphatase activity, but was inhibitory towards CAPP. Moreover, the divalent cations Cr 2+ , Mn 2+ , Fe 2+ , Ni 2+ , Cu 2+ and Zn 2+ were tested and all were found to be inhibitory towards both CAPP and basal phosphatase activities. By contrast, Cs + and Li + had almost no effect on CAPP, although both stimulated basal phosphatase activity. The effects of EDTA and EGTA were tested and it was observed that EDTA decreased CAPP activity in a dose-dependent fashion, but had no effect upon basal phosphatase activity. These results suggest that CAPP is a metal-dependent protein, but, because Ca 2+ inhibitied CAPP and EGTA was much less potent than EDTA in inhibiting CAPP, Ca 2+ is unlikely to be its metal cofactor.

Age- and brain region-dependent α-synuclein oligomerization is attributed to alterations in intrinsic enzymes regulating α-synuclein phosphorylation in aging monkey brains

“…The above results show that the synthetic C2 ceramide can reduce α-syn phosphorylation and oligomerization in brain extracts. Since ceramide has been shown to activate PP2A [ 37 ], it is likely that in those brain regions with reduced PP2A activity there is a reduction in levels of naturally occurring ceramide. We measured ceramide in brain extracts and found that the levels of ceramide in the striatum and hippocampus were much lower than those in the cerebellum and occipital cortex.…”

“…In the brains of patients with PD, there is a reduction in GCase activity and ceramide levels [ 38 ]. Because ceramide is a hydrolytic product of GlcCer when it is catalyzed by GCase, and is an activator of PP2A [ 37 ], its reduction due to impaired GCase activity would attenuate PP2A activity. In accordance with the changes in PP2A activity, the levels of ceramide and activity of GCase were lower in extracts from the striatum and hippocampus than in those from the cerebellum and occipital cortex.…”

“…The accumulation of oligomeric α-syn can alter the activity of GCase by modulating its transport from the endoplasmic reticulum to the lysosome [ 34 - 36 ]. Additionally, it may also enable an increase in α-syn phosphorylation by reducing the activity of PP2A via decreased production of ceramide, an activator of PP2A [ 37 ]. While there is evidence suggesting an inverse relationship between the reduced activity of GCase and increased levels of ceramide in the brains of patients with PD [ 38 ], variations in GCase in the aging brain and their potential links to the age- and brain region-dependent α-syn oligomerization remain unknown.…”

PACAP and C2‐ceramide generate different AP‐1 complexes through a MAP‐kinase‐dependent pathway: involvement of c‐Fos in PACAP‐induced Bcl‐2 expression

“…In agreement with these data, it has been shown that CREB is a target of PP2A (Johannessen et al . 2003) and that ceramides are potent activators of PP2A (Galadari et al . 2001).…”

Blood Plasma of Patients with Parkinson’s Disease Increases Alpha-Synuclein Aggregation and Neurotoxicity

“…GCase activity and ceramide levels are reduced in PD patient brains [16]. Since ceramide is a natural activator of PP2A [17], its reduction reduces PP2A activity, which indirectly promotes α -syn phosphorylation.…”