Regulation of Tyrosine Hydroxylase Expression and Phosphorylation in Dopamine Transporter-Deficient Mice

Abstract

Tyrosine hydroxylase (TH) and dopamine transporters (DATs) regulate dopamine (DA) neurotransmission at the biosynthesis and reuptake steps, respectively. Dysfunction or loss of these proteins occurs in impaired locomotor or addictive behavior, but little is known about the influence of DAT expression on TH function. Differences in TH phosphorylation, DA tissue content, L-DOPA biosynthesis, and DA turnover exist between the somatodendritic and terminal field compartments of nigrostriatal and mesoaccumbens pathways. We examined whether differential DAT expression affects these compartmental differences in DA regulation by comparing TH expression and phosphorylation at ser31 and ser40. In heterozygous DAT knockout (KO) (+/−) mice, DA tissue content and DA turnover were unchanged relative to wild-type mice, despite a 40% reduction in DAT protein expression. In DAT KO (−/−) mice, DA turnover increased in all DA compartments, but DA tissue content decreased (90–96%) only in terminal fields. TH protein expression and phosphorylation were differentially affected within DA pathway compartments by relative expression of DAT. TH protein decreased (~74%), though to a significantly lesser extent than DA, in striatum and nucleus accumbens (NAc) in DAT −/− mice, with no decrease in substantia nigra or ventral tegmental area. Striatal ser31 TH phosphorylation and recovery of DA relative to TH protein expression in DAT +/− and DAT −/− mice decreased, whereas ser40 TH phosphorylation increased ~2- to 3-fold in striatum and NAc of DAT −/− mice. These results suggest that DAT expression affects TH expression and phosphorylation largely in DA terminal field compartments, further corroborating evidence for dichotomous regulation of TH between somatodendritic and terminal field compartments of the nigrostriatal and mesoaccumbens pathways.

Autism-linked dopamine transporter mutation alters striatal dopamine neurotransmission and dopamine-dependent behaviors

“…Therefore, we measured changes in phosphorylation of TH in Ser31 (pTH Ser31) and found that pTH Ser31 was reduced in DAT T356M +/+ mice relative to WT mice ( Figure 2C) (n = 12 from 4 animals for each genotype; P = 0.0172, Student's 2-tailed t test), with no change in total TH expression. Decreased TH phosphorylation could be a result of continuous stimulation of the D 2 R due to a reduced DA clearance in the DAT T356M +/+ mouse, which has been shown to decrease D 2 R function (45,46). It is also consistent with previous literature demonstrating reduced TH Ser31 phosphorylation as well as increased extracellular DA levels in animals with loss of the DAT (46).…”

Enhanced dopamine D2 autoreceptor function in the adult prefrontal cortex contributes to dopamine hypoactivity following adolescent social stress

“…Together, these results suggest that decreased synthesis does not contribute to dopaminergic hypofunction in the adult mPFC caused by adolescent social defeat. However, further studies examining possible changes to phosphorylation of other serine residues would be of benefit in confirming the current findings, given pSer19 and 31 have been shown to play prominent roles in regulating TH activity (Damanhuri et al., ; Salvatore, Calipari, & Jones, ).…”

A dopaminergic mechanism of antipsychotic drug efficacy, failure, and failure reversal: the role of the dopamine transporter

“…Therefore, we further investigated the effect of APDs on DAT regulation. We estimated the putative coupling of striatal TH and DAT expression, which are coregulated [36]. We found no linear relationship between the TH and DAT expression levels in the control animals ( Fig.…”