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

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