Stability and dynamics of VBC-HIF complexes under normoxic and hypoxic conditions

MERLINO, ALICIA; MATHÓ, CECILIA; SANSÓ, GABRIELA; PENNISI, PATRICIA; COITIÑO, ELENA LAURA

Santiago

Congreso; 10th Congress of the World Association of Theoretical and Computational Chemists, WATOC; 2014

Stability and dynamics of VBC-HIF complexes under normoxic and hypoxic conditions Alicia Merlinoa, Cecilia Mathob, Gabriela Sansób, Patricia Pennisib, E. Laura Coitiñoa aLaboratorio de Química Teórica y Computacional, Instituto de Química Biológica, Facultad de Ciencias, Universidad de la República, Montevideo, Uruguay; e-mail: amerlino@fcien.edu.uy; bCentro de Investigaciones Endocrinológicas ?Dr. César Bergadá? (CEDIE), CONICET?FEI?División de Endocrinología, Hospital de Niños Ricardo Gutiérrez, Buenos Aires, Argentina; e-mail: cmatho@cedie.org.ar Abstract The α subunit of the Hypoxia inducible factor (HIF-1α) plays an important role in oxygen sensing, exhibiting a highly conserved Pro564 hydroxylated in normoxia by prolyl hydroxylases [1]. The multiprotein complex formed by VHL, Elonguins B and C (VBC) binds to HIF-1α, causing its poliubiquitination, thus targeting its degradation by the 26S proteasome. Under hypoxic conditions hydroxylation is inhibited, diminishing its affinity for VBC, allowing HIF-1α accumulation and migration to the nucleus. In the nucleus, HIF-1α/1β dimers form an active transcription factor for genes involved in energetic metabolism, angiogenesis and apoptosis, mechanisms involved in the development of the von Hippel-Lindau disease. Previous studies show that the HIF-VBC complex is stable in normoxia, while its occurrence in hypoxia is controversial [2,3]. The aim of this study is to elucidate this aspect by estimating the binding free energies for the complexes HIF-1α (Hyp564/Pro564) using MM/PB(GB)SA approaches. Based on the crystallographic structure of the VBC-HIF complex (PDB ID1LQB), the structure and dynamics in solution was modeled by classical simulations for both variants of HIF 1α, with particular focus on characterizing the hydrogen bond network (EdH) and the role of water molecules present in the pVHL-HIF interface. The results show that both complexes are thermodynamically favorable. However the HypPro substitution in HIF-pVHL interface alters the structure and dynamics of protein-protein and protein-water EdHs, resulting in a marked destabilization of the complex consistent with the experiments of Hon et al [2]. Besides providing information on the atomic level VBC-HIF recognition under normoxic/hypoxic conditions, this study has enabled the validation of the use of MM(GB)SA approaches for calculating the binding affinity of VBC-HFI complexes. This finding will be useful for future prediction of the effects of pVHL mutations that are related with pathological conditions. Acknowledgments: AM acknowledges PEDECIBA for financial support, CM has a PhD Fellowship from CONICET Argentina. This work was supported by the following grants: PIP 11220080101905 CONICET (awarded to PP) and STAN ST240, ST241 CONICET (awarded to GS). References: [1] D. A. Chan, P. D. Sutphin, S. E. Yen, et al, Mol. Cell Biol. 25 (2005) 6415. [2] W. C. Hon, M. I. Wilson, K. Harlos, et al, Nature, 417 (2002) 975. [3] J. H. Min, H. Yang, M. Ivan, et al, Science, 296 (2002) 1886.