Phosphorylation and cell cycle-dependent regulation of Na+/H+ exchanger regulatory factor-1 by Cdc2 kinase.
Na(+)/H(+) exchanger regulatory factor (NHERF)-1 is a PDZ domain-containing adaptor protein known to bind to various receptors, channels, cytoskeletal elements, and cytoplasmic signaling proteins. We report here that the phosphorylation state of NHERF-1 is profoundly regulated by the cell cycle: NHERF-1 in HeLa cells is hyperphosphorylated in mitosis phase and much less phosphorylated at other points of the cell cycle. This mitosis phase-dependent phosphorylation of NHERF-1 could be blocked by roscovitine, consistent with phosphorylation by cyclin-dependent kinases. In vitro studies with purified NHERF-1 fusion proteins and purified kinases revealed that NHERF-1 was robustly phosphorylated by the cyclin-dependent kinase Cdc2. In contrast, the NHERF-1 relative NHERF-2 was not phosphorylated at all by Cdc2. NHERF-1 possesses two serines (Ser(279) and Ser(301)) that conform to the SPX(K/R) motif preferred for phosphorylation by Cdc2. Mutation of either of these serines reduced Cdc2-mediated phosphorylation of NHERF-1 in vitro, and mutation of both residues together completely abolished Cdc2-mediated phosphorylation. When the S279A/S301A NHERF-1 mutant was expressed in cells, it failed to exhibit the mitosis phase-dependent phosphorylation observed with wild-type NHERF-1. Mutation of both Ser(279) and Ser(301) to aspartate, to mimic Cdc2 phosphorylation of NHERF-1, resulted in a NHERF-1 mutant with a markedly impaired ability to oligomerize in vitro. Similarly, endogenous NHERF-1 from lysates of mitosis phase HeLa cells exhibited a markedly reduced ability to oligomerize relative to endogenous NHERF-1 from lysates of interphase HeLa cells. Mitosis phase NHERF-1 furthermore exhibited the ability to associate with Pin1, a WW domain-containing peptidylprolyl isomerase that does not detectably bind to NHERF-1 in interphase lysates. The association of NHERF-1 with Pin1 facilitated dephosphorylation of NHERF-1, as shown in experiments in which cellular Pin1 activity was blocked by the selective inhibitor juglone. These data reveal that cellular NHERF-1 is phosphorylated during mitosis phase by Cdc2 at Ser(279) and Ser(301) and that this phosphorylation regulates NHERF-1 oligomerization and association with Pin1.
He
J
J
Department of Pharmacology, Rollins Research Center, Emory University School of Medicine, Atlanta, Georgia 30322, USA.
Lau
A G
AG
Yaffe
M B
MB
Hall
R A
RA
D000595:Amino Acid Sequence; D016203:CDC2 Protein Kinase / Q000502:physiology*; D002453:Cell Cycle; D006367:HeLa Cells; D006801:Humans; D008938:Mitosis; D008969:Molecular Sequence Data; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000502:physiology; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D017923:Sodium-Hydrogen Exchangers
D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; C093376:sodium-hydrogen exchanger regulatory factor; D016203:CDC2 Protein Kinase; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase