Targeted disruption of the mouse NHERF-1 gene promotes internalization of proximal tubule sodium-phosphate cotransporter type IIa and renal phosphate wasting.

Na+/H+ exchanger regulatory factor (NHERF)-1 and NHERF-2, two structurally related protein adapters containing tandem PSD-95/Discs large/ZO-1 (PDZ) domains, were identified as essential factors for protein kinase A-mediated inhibition of the sodium-hydrogen exchanger, NHE3. NHERF-1 and NHERF-2 also bound other cellular targets including the sodium-phosphate cotransporter type IIa encoded by the NPT2 gene. Targeted disruption of the mouse NHERF-1 gene eliminated NHERF-1 expression in kidney and other tissues of the mutant mice without altering NHERF-2 levels in these tissues.

N-terminal PDZ domain is required for NHERF dimerization.

NHERF, a 55 kDa PDZ-containing protein, binds receptors and ion transporters to mediate signal transduction at the plasma membrane. Recombinant NHERF demonstrated an apparent size of 150 kDa on gel filtration, which could be reduced to approximately 55 kDa by protein denaturing agents, consistent with the formation of NHERF dimers. Biosensor studies established the time- and concentration-dependent dimerization of NHERF.

Signal complex regulation of renal transport proteins: NHERF and regulation of NHE3 by PKA.

The activity of the sodium/hydrogen exchanger 3 (NHE3) isoform of the sodium/hydrogen exchanger in the brush-border membrane of the renal proximal tubule is tightly regulated. Recent biochemical and cellular experiments have established the essential requirement for a new class of regulatory factors, sodium/hydrogen exchanger regulatory factor (NHERF) and NHERF-like proteins, in cAMP-mediated inhibition of NHE3 activity. NHERF is the first PSD-95/Dlg/ZO-1 (PDZ) motif-containing protein localized to apical membranes and appears to facilitate cAMP-dependent protein kinase A (PKA) phosphorylation of NHE3 by interacting with the cytoskeleton to target a multiprotein complex to the brush-border membrane.

Assembly of signaling complexes by the sodium-hydrogen exchanger regulatory factor family of PDZ-containing proteins.

The sodium-hydrogen exchanger regulatory factor (NHERF) was first identified as an essential cofactor for cyclic AMP-mediated inhibition of the epithelial isoform of rabbit kidney sodium-hydrogen exchanger (NHE3). More recent work shows that NHERF constitutes a family of PSD-95/DIg/ZO-1 (PDZ) domain-containing adapter proteins, only some of which associate with the NHE3 antiporter. Other targets of the NHERF proteins include members of the ezrin-radixin-moesin family of cytoskeletal proteins.

Oocyte activation and passage through the metaphase/anaphase transition of the meiotic cell cycle is blocked in clams by inhibitors of HMG-CoA reductase activity.

Cell cycle progression for postembryonic cells requires the activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-R), the enzyme which catalyzes the production of the isoprenoid precursor, mevalonate. In this study, we examine the requirements of HMG-R activity for cell cycle progression during the meiotic and early mitotic divisions using oocytes and dividing embryos from the surf clam, Spisula solidissima. Using two different inhibitors of HMG-R, we find that the activity of this enzyme appears to be required at three distinct points of the cell cycle during meiosis.