Reciprocal influence of the p53 and the hypoxic pathways

When cells sense a decrease in oxygen availability (hypoxia), they develop adaptive responses in order to sustain this condition and survive. If hypoxia lasts too long or is too severe, the cells eventually die. Hypoxia is also known to modulate the p53 pathway, in a manner dependent or not of HIF-1 (hypoxia-inducible factor-1), the main transcription factor activated by hypoxia. The p53 protein is a transcription factor, which is rapidly stabilised by cellular stresses and which has a major role in the cell responses to these stresses. The aim of this review is to compile what has been reported until now about the interconnection between these two important pathways. Indeed, according to the cell line, the severity and the duration of hypoxia, oxygen deficiency influences very differently p53 protein level and activity. Conversely, p53 is also described to affect HIF-1α stability, one of the two subunits of HIF-1, and HIF-1 activity. The direct and indirect interactions between HIF-1α and p53 are described as well as the involvement in this complex network of their respective ubiquitin ligases von Hippel Lindau protein and murine double minute 2. Finally, the synergistic or antagonistic effects of p53 and HIF-1 on some important cellular pathways are discussed

The High-Risk Type 1 Diabetes HLA-DR and HLA-DQ Polymorphisms Are Differentially Associated With Growth and IGF-I Levels in Infancy: The Cambridge Baby Growth Study.

OBJECTIVE: This study explored the link between HLA polymorphisms that predispose to type 1 diabetes and birth size, infancy growth, and/or circulating IGF-I in a general population-based birth cohort. RESEARCH DESIGN AND METHODS: The Cambridge Baby Growth Study is a prospective observational birth cohort study that recruited 2,229 newborns for follow-up in infancy. Of these, 612 children had DNA available for genotyping single nucleotide polymorphisms in the HLA region that capture the highest risk of type 1 diabetes: rs17426593 for DR4, rs2187668 for DR3, and rs7454108 for DQ8. Multivariate linear regression models at critical ages (cross-sectional) and mixed-effects models (longitudinal) were performed under additive genetic effects to test for associations between HLA polymorphisms and infancy weight, length, skinfold thickness (indicator of adiposity), and concentrations of IGF-I and IGF-binding protein-3 (IGFBP-3). RESULTS: In longitudinal models, the minor allele of rs2187668 tagging DR3 was associated with faster linear growth (P = 0.007), which was more pronounced in boys (P = 3 × 10-7) than girls (P = 0.07), and was also associated with increasing IGF-I (P = 0.002) and IGFBP-3 (P = 0.003) concentrations in infancy. Cross-sectionally, the minor alleles of rs7454108 tagging DQ8 and rs17426593 tagging DR4 were associated with lower IGF-I concentrations at age 12 months (P = 0.003) and greater skinfold thickness at age 24 months (P = 0.003), respectively. CONCLUSIONS: The variable associations of DR4, DR3, and DQ8 alleles with growth measures and IGF-I levels in infants from the general population could explain the heterogeneous growth trajectories observed in genetically at-risk cohorts. These findings could suggest distinct mechanisms involving endocrine pathways related to the HLA-conferred type 1 diabetes risk.This work was supported by the Medical Research Council (MR/K50127X/1) and the Raymond & Beverly Sackler Foundation. The CBGS has been funded by the European Union Framework 5 (QLK4-1999-01422), the Medical Research Council (7500001180, G1001995, U106179472) and the World Cancer Research Fund International (2004/03). K.K.O. is supported by the Medical Research Council (MC_UU_12015/2). DBD is supported by funding from the Innovative Medicines Initiative 2 Joint Undertaking under grant agreement No 115797 (INNODIA) and No 945268 (INNODIA HARVEST)