Sprouty2 Protein Regulates Hypoxia-inducible Factor-α (HIFα) Protein Levels and Transcription of HIFα-responsive Genes.
The α-subunits of hypoxia-inducible factors (HIF1α and HIF2α) promote transcription of genes that regulate glycolysis and cell survival and growth. Sprouty2 (Spry2) is a modulator of receptor tyrosine kinase signaling and inhibits cell proliferation by a number of different mechanisms. Because of the seemingly opposite actions of HIFα subunits and Spry2 on cellular processes, we investigated whether Spry2 regulates the levels of HIF1α and HIF2α proteins. In cell lines from different types of tumors in which the decreased protein levels of Spry2 have been associated with poor prognosis, silencing of Spry2 elevated HIF1α protein levels. Increases in HIF1α and HIF2α protein levels due to silencing of Spry2 also up-regulated HIFα target genes. Using HIF1α as a prototype, we show that Spry2 decreases HIF1α stability and enhances the ubiquitylation of HIF1α by a von Hippel-Lindau protein (pVHL)-dependent mechanism. Spry2 also exists in a complex with HIF1α. Because Spry2 can also associate with pVHL, using a mutant form of Spry2 (3P/3A-Spry2) that binds HIF1α, but not pVHL, we show that WT-Spry2, but not the 3P/3A-Spry2 decreases HIF1α protein levels. In accordance, expression of WT-Spry2, but not 3P/3A-Spry2 results in a decrease in HIF1α-sensitive glucose uptake. Together our data suggest that Spry2 acts as a scaffold to bring more pVHL/associated E3 ligase in proximity of HIF1α and increase its ubiquitylation and degradation. This represents a novel action for Spry2 in modulating biological processes regulated by HIFα subunits.
From the Department of Molecular Pharmacology and Therapeutics, Loyola University Chicago, Maywood, Illinois 60153, and.
Kristin C
KC
Hicks
the Albany College of Pharmacy and Health Sciences, Albany, New York 12208 tarun.patel@acphs.edu.
Tarun B
TB
Patel
D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D055550:Protein Stability; D014158:Transcription, Genetic; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism; D000099162:Endothelial PAS Domain-Containing Protein 1
D051792:Basic Helix-Loop-Helix Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D044767:Ubiquitin-Protein Ligases; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D000099162:Endothelial PAS Domain-Containing Protein 1; C497442:HIF1A protein, human; C485561:SPRY2 protein, human; C497446:VHL protein, human
Sprouty2; glucose uptake; hepatocellular carcinoma; hypoxia; hypoxia-inducible factor (HIF); signaling; ubiquitylation (ubiquitination)