Modulation of D[sub.3]R Splicing, Signaling, and Expression by D[sub.1]R through PKA→PTB Phosphorylation

The D[sub.1]R and D[sub.3]R receptors functionally and synergistically interact in striatonigral neurons. Dopaminergic denervation turns this interaction antagonistic, which is correlated with a decrement in D[sub.3]nf isoform and an increment in D[sub.3]R membranal expression. The mechanisms of such changes in D[sub.3]R are attributed to the dysregulation of the expression of their isoforms. The cause and mechanism of this phenomenon remain unknown. Dopaminergic denervation produces a decrement in D[sub.1]R and PKA activity; we propose that the lack of phosphorylation of PTB (regulator of alternative splicing) by PKA produces the dysregulation of D[sub.3]R splicing and changes D[sub.3]R functionality. By using in silico analysis, we found that D[sub.3]R mRNA has motifs for PTB binding and, by RIP, co-precipitates with PTB. Moreover, D[sub.1]R activation via PKA promotes PTB phosphorylation. Acute and 5-day D[sub.1]R blockade decreases the expression of D[sub.3]nf mRNA. The 5-day treatment reduces D[sub.3]R, D[sub.3]nf, and PTB protein in the cytoplasm and increases D[sub.3]R in the membrane and PTB in the nucleus. Finally, the blockade of D[sub.1]R mimics the effect of dopaminergic denervation in D[sub.1]R and D[sub.3]R signaling. Thus, our data indicate that through PKA→PTB, D[sub.1]R modulates D[sub.3]R splicing, expression, and signaling, which are altered during D[sub.1]R blockade or the lack of stimulation in dopaminergic denervation.