A Conserved Serine of Heterogeneous Nuclear Ribonucleoprotein L (hnRNP L) Mediates Depolarization-regulated Alternative Splicing of Potassium Channels

• Published in: The Journal of biological chemistry Vol. 287; no. 27; pp. 22709 - 22716
• Main Authors: Liu, Guodong, Razanau, Aleh, Hai, Yan, Yu, Jiankun, Sohail, Muhammad, Lobo, Vincent G., Chu, Jiayou, Kung, Sam K.P., Xie, Jiuyong
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 29.06.2012; American Society for Biochemistry and Molecular Biology
• Subjects: Alternative Splicing; Alternative Splicing - physiology; Amino Acid Sequence; Animals; Base Sequence; Calcium Calmodulin-dependent Protein Kinase (CaMK); Calcium Signaling - physiology; Calcium-Calmodulin-Dependent Protein Kinase Type 4 - metabolism; Cells, Cultured; Depolarization; Exons - genetics; Heterogeneous Nuclear Ribonucleoprotein L; Heterogeneous-Nuclear Ribonucleoprotein L - genetics; Heterogeneous-Nuclear Ribonucleoprotein L - metabolism; Large-Conductance Calcium-Activated Potassium Channel alpha Subunits - genetics; Membrane Potentials - physiology; Molecular Sequence Data; mRNA; Nuclear Proteins - metabolism; Phosphorylation; Phosphorylation - physiology; Pituitary Gland - cytology; Potassium Channels; Rats; Ribonucleoproteins - metabolism; RNA; Serine - metabolism; Splicing Factor U2AF; U2AF65; Potassium Channels; Depolarization; Phosphorylation; Alternative Splicing; Heterogeneous Nuclear Ribonucleoprotein L; Calcium Calmodulin-dependent Protein Kinase (CaMK); mRNA; U2AF65
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.357343

Molecular mechanisms of gene regulation underlying the activity-dependent long term changes of cellular electrical properties, such as those during memory, are largely unknown. We have shown that alternative splicing can be dynamically regulated in response to membrane depolarization and Ca2+/calmodulin-dependent protein kinase IV (CaMKIV) activation, through special CaM kinase responsive RNA elements. However, proteins that mediate this regulation and how they are affected by CaMKIV are not known. Here we show that the regulation of the stress axis-regulated exon of the Slo1 potassium channel transcripts by membrane depolarization requires a highly conserved CaMKIV target serine (Ser-513) of the heterogeneous ribonucleoprotein L. Ser-513 phosphorylation within the RNA recognition motif 4 enhanced heterogeneous ribonucleoprotein L interaction with the CaMKIV-responsive RNA element 1 of stress axis-regulated exon and inhibited binding of the large subunit of the U2 auxiliary factor U2AF65. Both of these activities were abolished by a S513A mutation. Thus, through Ser-513, membrane depolarization/calcium signaling controls a critical spliceosomal assembly step to regulate the variant subunit composition of potassium channels. Background: Excitable cells show activity-dependent alternative splicing of ion channels. Results: CaMKIV phosphorylates hnRNP L at Ser-513, which is essential for depolarization-repression of a Slo1 potassium channel exon and splicing factor U2AF65. Conclusion: Depolarization controls alternative splicing of Slo1 channels through Ser-513 phosphorylation and inhibition of U2AF65. Significance: This provides the first direct link between depolarization/CaMKIV and the constitutive spliceosome.