title: Phosphorylation Regulates Id2 Degradation and Mediates the Proliferation of Neural Precursor Cells.
abstract: Inhibitor of DNA binding proteins (Id1-Id4) function to inhibit differentiation and promote proliferation of many different cell types. Among the Id family members, Id2 has been most extensively studied in the central nervous system (CNS). Id2 contributes to cultured neural precursor cell (NPC) proliferation as well as to the proliferation of CNS tumors such as glioblastoma that are likely to arise from NPC-like cells. We identified three phosphorylation sites near the N-terminus of Id2 in NPCs. To interrogate the importance of Id2 phosphorylation, Id2(-/-) NPCs were modified to express wild type (WT) Id2 or an Id2 mutant protein that could not be phosphorylated at the identified sites. We observed that NPCs expressing this mutant lacking phosphorylation near the N-terminus had higher steady-state levels of Id2 when compared to NPCs expressing WT Id2. This elevated level was the result of a longer half-life and reduced proteasome-mediated degradation. Moreover, NPCs expressing constitutively de-phosphorylated Id2 proliferated more rapidly than NPCs expressing WT Id2, a finding consistent with the well-characterized function of Id2 in driving proliferation. Observing that phosphorylation of Id2 modulates the degradation of this important cell-cycle regulator, we sought to identify a phosphatase that would stabilize Id2 enhancing its activity in NPCs and extended our analysis to include human glioblastoma-derived stem cells (GSCs). We found that expression of the phosphatase PP2A altered Id2 levels. Our findings suggest that inhibition of PP2A may be a novel strategy to regulate the proliferation of normal NPCs and malignant GSCs by decreasing Id2 levels. Stem Cells 2016;34:1321-1331.
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Pharmacology and Toxicology, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Jaclyn M
authors.initials: JM
authors.lastname: Sullivan
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Pediatrics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Havrda
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Arminja N
authors.initials: AN
authors.lastname: Kettenbach
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Brenton R
authors.initials: BR
authors.lastname: Paolella
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Pediatrics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Zhonghua
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.|Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Gerber
authors.affiliation: Pharmacology and Toxicology, Norris Cotton Cancer Center, One Medical Center Drive, Lebanon, NH, 03756.|Department of Pediatrics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.|Department of Genetics, Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA.
authors.forename: Mark A
authors.initials: MA
authors.lastname: Israel
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002453:Cell Cycle; D049109:Cell Proliferation; D005909:Glioblastoma / Q000473:pathology; D051797:Inhibitor of Differentiation Protein 2 / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D014411:Neoplastic Stem Cells / Q000378:metabolism / Q000473:pathology; D058953:Neural Stem Cells / Q000166:cytology* / Q000378:metabolism*; D010766:Phosphorylation; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000378:metabolism; D059748:Proteolysis
chemical_list: C497452:Idb2 protein, mouse; D051797:Inhibitor of Differentiation Protein 2; D054648:Protein Phosphatase 2; D046988:Proteasome Endopeptidase Complex
keywords: Cancer stem cells; Cellular proliferation; Glioma; Neoplastic stem cell biology; Neural stem cell; Progenitor cells; Tissue-specific stem cells; Transcription factors