Cell-type-specific regulation of degradation of hypoxia-inducible factor 1 alpha: role of subcellular compartmentalization.
The hypoxia-inducible factor-1 alpha (HIF-1 alpha) is a transcription factor that mediates adaptive cellular responses to decreased oxygen availability (hypoxia). At normoxia, HIF-1 alpha is targeted by the von Hippel-Lindau tumor suppressor protein (pVHL) for degradation by the ubiquitin-proteasome pathway. In the present study we have observed distinct cell-type-specific differences in the ability of various tested pVHL-interacting subfragments to stabilize HIF-1 alpha and unmask its function at normoxia. These properties correlated with differences in subcellular compartmentalization and degradation of HIF-1 alpha. We observed that the absence or presence of nuclear localization or export signals differently affected the ability of a minimal HIF-1 alpha peptide spanning residues 559 to 573 of mouse HIF-1 alpha to stabilize endogenous HIFalpha and induce HIF-driven reporter gene activity in two different cell types (primary mouse endothelial and HepG2 hepatoma cells). Degradation of HIF-1 alpha occurred mainly in the cytoplasm of HepG2 cells, whereas it occurs with equal efficiency in nuclear and cytoplasmic compartments of primary endothelial cells. Consistent with these observations, green fluorescent protein-HIF-1 alpha is differently distributed during hypoxia and reoxygenation in hepatoma and endothelial cells. Consequently, we propose that differential compartmentalization of degradation of HIF-1 alpha and the subcellular distribution of HIF-1 alpha may account for cell-type-specific differences in stabilizing HIF-1 alpha protein levels under hypoxic conditions.
Zheng
Xiaowei
X
Department of Cell and Molecular Biology, Karolinska Institutet, S-171 77 Stockholm, Sweden.
Ruas
Jorge L
JL
Cao
Renhai
R
Salomons
Florian A
FA
Cao
Yihai
Y
Poellinger
Lorenz
L
Pereira
Teresa
T
D000595:Amino Acid Sequence; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000378:metabolism; D002417:Cattle; D002451:Cell Compartmentation; D015687:Cell Hypoxia; D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D015696:Gene Products, tat / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008954:Models, Biological; D018919:Neovascularization, Physiologic; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D051794:Von Hippel-Lindau Tumor Suppressor Protein / Q000378:metabolism
D015696:Gene Products, tat; C497442:HIF1A protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D051794:Von Hippel-Lindau Tumor Suppressor Protein; D046988:Proteasome Endopeptidase Complex; C497446:VHL protein, human