A consensus CaMK IV-responsive RNA sequence mediates regulation of alternative exons in neurons

Abstract

Neurons make extensive use of alternative pre-mRNA splicing to regulate gene expression and diversify physiological responses. We showed previously in a pituitary cell line that the Ca ++ /calmodulin-dependent protein kinase CaMK IV specifically repressed splicing of the BK channel STREX exon. This repression is dependent on a CaMK IV-responsive RNA element (CaRRE) within the STREX 3 0 splice site. Here, we report that similar Ca ++ regulation of splicing, mediated by L-type calcium channels and CaM kinase IV, occurs in cultured neurons and in the brain. We identify a critical CaRRE motif (CACATNRTTAT) that is essential for conferring CaMK IV repression on an otherwise constitutive exon. Additional Ca ++ -regulated exons that carry this consensus sequence are also identified in the human genome. Thus, the Ca ++ /CaMK IV pathway in neurons controls the alternative splicing of a group of exons through this short CaRRE consensus sequence. The functions of some of these exons imply that splicing control through the CaMK IV pathway will alter neuronal activity.

Control of alternative pre-mRNA splicing by Ca++ signals

“…These stimuli can either promote or repress the inclusion of an exon (Table 1). Importantly, their effects on splicing can be inhibited by the L-type Ca ++ channel blockers verapamil, nifedipine or nimodipine [95,96,102,103,107], by the NMDA receptor antagonist AP5 or MK-801 [84,95,96,103], by the Ca ++ /calmodulin-dependent protein kinase inhibitors KN93 or KN62 [84,95,96,104,105], or by the cell permeable Ca ++ chelator BAPTA-AM [101,108]. Together, these observations strongly support the regulation of alternative pre-mRNA splicing by variations in intracellular Ca ++ levels.…”

“…In rat pituitary GH 3 cells and cerebellar neurons, addition of depolarizing concentrations of KCl leads to a decrease in transcripts containing the STREX exon [104,107] (Fig. 3).…”

“…Of the various Ca ++ signals that regulate splicing, those through the CaMK IV pathway have been the most intensively studied [104,105,107]. A prime example of the effect on splicing by this pathway is the BK channel STREX exon, one of the more than 10 alternative exons of the vertebrate Slo gene [19,[21][22][23][24][25][26][27][28][29][30][31][32][33][34][35] (Fig.…”

“…Inclusion of this exon confers higher voltage and Ca ++ sensitivity on the channel [24,[29][30][31]153], inhibition by PKA and oxidation [142,154], and sensitivity to glucocorticoids [143]. The exon is included in endocrine cells and neurons and enriched in the high frequency region of cochleae [22][23][24]84,107], contributing to the fine-tuning of hearing frequencies in birds and turtles [23,31]. Its inclusion is also regulated by steroid hormones in animals and by membrane depolarization in cultured cells [24,104,107,[155][156][157].…”

“…The exon is included in endocrine cells and neurons and enriched in the high frequency region of cochleae [22][23][24]84,107], contributing to the fine-tuning of hearing frequencies in birds and turtles [23,31]. Its inclusion is also regulated by steroid hormones in animals and by membrane depolarization in cultured cells [24,104,107,[155][156][157]. Thus, the STREX exon inclusion is inducible by external stimuli and the regulation may modulate multiple properties of the BK channels.…”