Journal of Neurogastroenterology and Motility
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Korean J Physiol Pharmacol 2018 Jan; 22(1): 91-99
Kyu Pil Lee1, Hyun Jin Kim2,*, and Dongki Yang3,*
Functional identification of protein phosphatase 1-binding consensus residues in NBCe1-B
1Laboratory of Physiology, College of Veterinary Medicine, Chungnam National University, Daejeon 34134, 2Department of Physiology, School of Medicine, Sungkyunkwan University, Suwon 16419, 3Department of Physiology, College of Medicine, Gachon University, Incheon 21999, Korea
Protein phosphatase 1 (PP1) is involved in various signal transduction mechanisms as an extensive regulator. The PP1 catalytic subunit (PP1c) recognizes and binds to PP1-binding consensus residues (FxxR/KxR/K) in NBCe1-B. Consequently, we focused on identifying the function of the PP1-binding consensus residue, 922FMDRLK927, in NBCe1-B. Using site-directed mutagenesis and co-immunoprecipitation assays, we revealed that in cases where the residues were substituted (F922A, R925A, and K927A) or deleted (deletion of amino acids 922-927), NBCe1-B mutants inhibited PP1 binding to NBCe1-B. Additionally, by recording the intracellular pH, we found that PP1-binding consensus residues in NBCe1-B were not only critical for NBCe1-B activity, but also relevant to its surface expression level. Therefore, we reported that NBCe1-B, as a substrate of PP1, contains these residues in the C-terminal region and that the direct interaction between NBCe1-B and PP1 is functionally critical in controlling the regulation of the HCO3 transport. These results suggested that like IRBIT, PP1 was another novel regulator of HCO3 secretion in several types of epi-thelia.
Keyword : HCO3- secretion, IRBIT, NBCe1-B, Protein phosphatase 1, SPAK, WNK