title: Akt1 phosphorylates Nicastrin to regulate its protein stability and activity.
abstract: The gamma-secretase is a multiprotein complex that cleaves many type-I membrane proteins, such as the Notch receptor and the amyloid precursor protein. Nicastrin (NCT) is an essential component of the multimeric gamma-secretase complex and functions as a receptor for gamma-secretase substrates. In this study, we found that Akt1 markedly regulated the protein stability of NCT. Importantly, the kinase activity of Akt1 was essential for the inhibition of gamma-secretase activity through degradation of NCT. Notably, the protein level of endogenous NCT was higher in shAkt1-expressing cells than in shCon-expressing cells. Akt1 physically interacted with NCT and mediated its degradation through proteasomal and lysosomal pathways. We also found that Akt1 phosphorylates NCT at Ser437, resulting in a significant reduction in NCT protein stability. Importantly, a phospho-deficient mutation in NCT at Ser437 stabilized its protein levels. Collectively, our results reveal that Akt1 functions as a negative regulator of the gamma-secretase activity through phosphorylation and degradation of NCT. Generation of the amyloid peptide (A-beta) and the amyloid precursor protein (APP) intracellular domain (AICD) can happen by sequential proteolysis of APP by beta and gamma-secretase. The gamma-secretase complex consists of four essential proteins: presenilin (PS1 or PS2), presenilin enhancer 2 (PEN-2), anterior pharynx-defective 1 (APH-1), and the Nicastrin (NCT). NCT can interact and be phosphorylated by Akt1, and phosphorylated NCT promotes its proteasomal and lysosomal degradation. As a result, Akt1 plays role in reducing gamma-secretase activity through phosphorylation-dependent regulation of NCT protein degradation.
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Eun-Hye
authors.initials: EH
authors.lastname: Jo
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Ji-Seon
authors.initials: JS
authors.lastname: Ahn
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Jung-Soon
authors.initials: JS
authors.lastname: Mo
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Ji-Hye
authors.initials: JH
authors.lastname: Yoon
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Ann
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Hyeong-Jin
authors.initials: HJ
authors.lastname: Baek
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Hye-Jin
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Seol-Hee
authors.initials: SH
authors.lastname: Kim
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Mi-Yeon
authors.initials: MY
authors.lastname: Kim
authors.affiliation: Hormone Research Center, School of Biological Sciences and Technology, Chonnam National University, Gwangju, Korea.
authors.forename: Hee-Sae
authors.initials: HS
authors.lastname: Park
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000235:genetics / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D055550:Protein Stability; D059748:Proteolysis; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D016564:Amyloid beta-Protein Precursor; D008562:Membrane Glycoproteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; C413604:nicastrin protein; D010768:Phosphoserine; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt; D053829:Amyloid Precursor Protein Secretases; D046988:Proteasome Endopeptidase Complex
keywords: Akt1; Nicastrin; co-localization; lysosome; phosphorylation; proteasome