Inhibition of protein kinase (PK) Cδ attenuates methamphetamine‐induced dopaminergic toxicity via upregulation of phosphorylation of tyrosine hydroxylase at Ser⁴⁰ by modulation of protein phosphatase 2A and PKA

Abstract

Recently, we proposed that inhibition of protein kinase (PK) Cδ may be a useful target for protection against methamphetamine (MA)-induced dopaminergic toxicity. We demonstrated that treatment with MA resulted in a significant decrease in phosphorylation of tyrosine hydroxylase (TH) at Ser(40) in the striatum, but not in the phosphorylation of TH at Ser(31) . In the present study, treatment with rottlerin (1.5 or 3.0 μg, i.c.v, once a day for 5 days), a PKCδ inhibitor, or a PKCδ antisense oligonucleotide (ASO; 2.5 μg/μl, i.c.v., 3 times) significantly attenuated MA-induced reductions in the phosphorylation of TH at Ser(40) and in the expression of PKA in the striatum of mice. This attenuation was significantly counteracted by H89 (10 or 30 ng, i.c.v., 1 h after the last MA administration), a PKA inhibitor. Treatment with rottlerin or ASO significantly attenuated the MA-induced increase in protein phosphatase (PP) 2A activity. FTY720 (1 or 5 mg/kg, i.p., 1 h after the last MA administration), a PP2A activator, significantly reversed the recovery in TH phosphorylation mediated by inhibition of PKCδ after MA treatment. Both H89 and FTY720 counteracted the recovery of MA-induced behavioural impairments induced by PKCδ inhibition. The effects, mediated by rottlerin or ASO in MA-treated wild-type mice were comparable with those in MA-treated PKCδ(-/-) mice. However, neither inhibition of the mitogen-activated protein kinase subfamily (extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38) nor inhibition of calcium calmodulin kinase II significantly altered PKCδ inhibition-mediated attenuation of MA-induced impairment of TH phosphorylation. The results suggest that genetic or pharmacological inhibition of PKCδ requires modulation of PKA expression and/or PP2A activity to attenuate the impairment of TH phosphorylation at Ser(40) and behavioural activity induced by MA.

Tyrosine hydroxylase phosphorylation in vivo

“…Treatment of mice with methamphetamine resulted in a decrease in TH phosphorylation at Ser40 relative to TH protein levels in the striatum (Shin et al 2011). This correlated with an increase in PP2A activity most likely because of increased PKCdelta activity (Dang et al 2015). When a single high dose of LPS is administered to adult rats, Ser40 is dephosphorylated in the adrenal gland 24 h later and although PKA is still activated, this is overridden by a sustained increase in PP2A activity (Ong et al 2017b).…”

“…This correlated with an increase in PP2A activity most likely because of increased PKCdelta activity (Dang et al . ). When a single high dose of LPS is administered to adult rats, Ser40 is dephosphorylated in the adrenal gland 24 h later and although PKA is still activated, this is overridden by a sustained increase in PP2A activity (Ong et al .…”

L-Tyr-Induced Phosphorylation of Tyrosine Hydroxylase at Ser⁴⁰: An Alternative Route for Dopamine Synthesis and Modulation of Na⁺/K⁺-ATPase in Kidney Cells

“…We examined the phosphorylation status of TH because Ser 40 phosphorylation increases TH activity in neurons [10, 11]. The question in mind was: would increased availability of L-tyr affect the regulation of the enzyme responsible for its conversion to L-dopa?…”

“…In addition, our results showed for the very first time that TH phosphorylation at Ser 40 is also significantly increased when the cells were exposed to L-tyr. It is well known that TH is responsible for catalysis of the limiting step of DA synthesis, being activated by phosphorylation of different serine residues triggered by different bioactive molecules [9, 10, 11, 12, 13]. TH phosphorylation at Ser 40 increases TH activity and consequently DA production [29].…”

“…Regulatory phosphorylation of TH is considered one of the most critical mechanisms in the pathway that culminates in DA formation. TH phosphorylation at Ser 40 increases enzyme activity in vitro , in situ and in vivo [9, 10, 11]. Activation of TH by phosphorylation is responsible for maintaining the levels of DA and the other catecholamines in tissues prior to secretion [12, 13].…”