Disease relevance of NEDD4L

• Androgens differentially regulate the expression of NEDD4L transcripts in LNCaP human prostate cancer cells [1].
• The ubiquitin ligase NEDD4L is a candidate gene for essential hypertension on both functional and genetic grounds [2].
• The NEDD4L gene is located on human chromosome 18q21 within several blood pressure quantitative trait loci, including those for familial orthostatic hypotension, essential hypertension, pulse pressure, and systolic blood pressure response to postural challenge [3].

High impact information on NEDD4L

• They regulate the activity of enzymes (e.g., glycogen synthase kinase-3, ubiquitin ligase Nedd4-2, phosphomannose mutase-2) and transcription factors (e.g., forkhead transcription factor FKHRL1, beta-catenin, nuclear factor kappaB) [4].
• The binding of Nedd4-2 to TrkA through a PPXY motif leads to the ubiquitination and downregulation of TrkA [5].
• Phosphorylation of Nedd4-2 by Sgk1 regulates epithelial Na(+) channel cell surface expression [6].
• Here we show by expression studies in Xenopus laevis oocytes that the aldosterone-induced Sgk1 kinase interacts with the ubiquitin protein ligase Nedd4-2 in a PY motif-dependent manner and phosphorylates Nedd4-2 on Ser444 and, to a lesser extent, Ser338 [6].
• This disproportionate increase in cleavage was reproduced by expression of a dominant-negative Nedd4-2 or mutation of ENaC ubiquitination sites, interventions that disrupt ENaC endocytosis and lysosomal degradation [7].

Chemical compound and disease context of NEDD4L

• A search for transcripts whose levels increase following androgen treatment of LNCaP human prostate cancer cells led to the isolation of three new NEDD4L transcripts designated NEDD4Lf, NEDD4Lg and NEDD4Lh [1].

Biological context of NEDD4L

• Differential function of NEDD4L isoforms could prove significant in blood pressure regulation through an effect on ENaC-dependent sodium reabsorption [2].
• NEDD4L is a ubiquitin ligase that controls cell surface expression of kidney epithelial Na+ channels by ubiquitin-mediated endocytosis and lysosome targeting [3].
• One of the SNPs associated in African Americans is known to result in premature truncation of the NEDD4L protein [3].
• To test this hypothesis, we fine-mapped the NEDD4L region in 2 families with orthostatic hypotension, which we previously reported to be linked to human chromosome 18q21 but failed to implicate NEDD4L in these families [3].
• Thus, genetic variation in NEDD4L may play a role in the development or progression of some forms of abnormal blood pressure [3].

Anatomical context of NEDD4L

• We found that this interaction preserved the activity of the Sgk1-stimulated ENaC-dependent Na+ current while disrupting the interaction decreased ENaC density on the Xenopus laevis oocytes surface possibly by enhancing Nedd4-2-mediated ubiquitination that leads to ENaC degradation [8].
• Coexpression, in Fischer rat thyroid epithelia, of ENaC and Nedd4-2 cDNAs leads to a significant reduction in amiloride-sensitive currents, confirming a role in Na+ transport regulation [9].
• Immunohistochemistry in human small intestine revealed SGK1 colocalization with Nedd4-2 in villus enterocytes [10].
• In summary, these results suggest a novel mechanism for ENaC regulation in which AMPK promotes ENaC-Nedd4-2 interaction, thereby inhibiting ENaC by increasing Nedd4-2-dependent ENaC retrieval from the plasma membrane [11].
• Nedd4-2 is expressed in the mouse collecting duct, and overexpression of Nedd4-2 reduces endogenous ENaC activity in a collecting duct cell line [12].

Associations of NEDD4L with chemical compounds

• NEDD4L contains the WW and HECT domains seen in the NEDD4 gene family, but lacks the C2 domain in the N-terminus [13].
• These data provide new information on the structure and expression profile of NEDD4L-derived transcripts and identify specific isoforms of the NEDD4L ubiquitin ligase as proteins with potentially important roles in androgen action and prostate physiology [1].
• By targeting the epithelial sodium channel (ENaC) for degradation, NEDD4L is a significant determinant of sodium reabsorption in the distal nephron [2].
• Glutamate induces a current in Xenopus oocytes expressing EAAT1, but not in water-injected oocytes, which is decreased by co-expression of Nedd4-2, an effect reversed by additional co-expression of S422DSGK1, SGK3 and T308D,S473DPKB, but not K127NSGK1 [14].
• Using intrinsic tryptophan fluorescence imaging of WW domains, we found that Na(v)1.5 PY motif binds preferentially to the fourth WW domain of Nedd4-2 with a K(d) of approximately 55 muM [15].

Physical interactions of NEDD4L

• Conversely, silencing of Nedd4-2 by RNA interference stabilized SGK [16].
• Nedd4-2 functionally interacts with ClC-5: involvement in constitutive albumin endocytosis in proximal tubule cells [17].

Enzymatic interactions of NEDD4L

• Moreover, (S422D)SGK1 and SGK3 phosphorylate Nedd4-2 [10].
• SGK phosphorylates Nedd4-2, which reduces Nedd4-2 binding and inhibition of ENaC [16].
• Nedd4-2 ubiquitinates both TTYH2 and TTYH3 [18].

Regulatory relationships of NEDD4L

• Cardiac voltage-gated sodium channel Nav1.5 is regulated by Nedd4-2 mediated ubiquitination [19].
• When expressed in HEK-293 cells and studied using whole cell voltage clamping, the neuronal Na(v)1.2 and Na(v)1.3 were also downregulated by Nedd4-2 [15].
• RESULTS: Expression of ClC-Ka/barttin induced a slightly inwardly rectifying current that was significantly decreased upon coexpression of Nedd4-2, but not the catalytically inactive mutant C938SNedd4-2 [20].

Other interactions of NEDD4L

• Site-directed mutagenesis of the SGK1 phosphorylation sites in the Nedd4-2 protein (S382A,S468ANedd4-2) and in the EAAT1 protein (T482AEAAT1, T482DEAAT1) significantly blunts the effect of S422DSGK1 [14].
• 5. Interestingly, coexpression of WWP2 competed with the effect of Nedd4-2 [15].
• Pull-down experiments using fusion proteins bearing the PY motif of Na(v)1.2, Na(v)1.3, and Na(v)1.5 indicated that mouse brain Nedd4-2 binds to the Na(v) PY motif [15].
• Regulation of CLC-Ka/barttin by the ubiquitin ligase Nedd4-2 and the serum- and glucocorticoid-dependent kinases [20].
• Increased channel activity induced by WNK1 depends on SGK1 and the E3 ubiquitin ligase Nedd4-2 [21].

Analytical, diagnostic and therapeutic context of NEDD4L

• Using surface plasmon resonance spectrometry, we show that 14-3-3 inhibits the interaction between the WW domains of hNedd4-2 and the PY motif of the epithelial Na(+) channel, ENaC [22].
• We hypothesized that Nedd4-2 is a susceptibility gene for hypertension and screened 856 renal patients and healthy controls for mutations in a subset of exons of the human Nedd4-2 gene that are relevant for ENaC regulation by PCR/single-strand conformational polymorphism [23].
• Using in situ hybridization experiments, rat NEDD4L was predominantly expressed in distal nephron in a manner dependent on both sodium regimen and genetic background [24].
• Moreover, cellular AMPK activation significantly enhanced the interaction of the beta-ENaC subunit with Nedd4-2, as measured by co-immunoprecipitation assays in HEK-293 cells [11].
• Moreover, we studied by real-time reverse transcriptase-polymerase chain reaction the effect of vasopressin on proteins implicated in the regulation of ENaC (Nedd4-2, prostasin, Sgk1) [25].

References