|Nuclear magnetic resonance structure revealed that the human polyomavirus JC virus agnoprotein contains an α-helix encompassing the Leu/Ile/Phe-rich domain.|
Coric, P; Saribas, AS; Abou-Gharbia, M; Childers, W; White, MK; Bouaziz, S; Safak, M
Journal of virology
Agnoprotein is a small multifunctional regulatory protein required for sustaining the productive replication of JC virus (JCV). It is a mostly cytoplasmic protein localizing in the perinuclear area and forms highly stable dimers/oligomers through a Leu/Ile/Phe-rich domain. There have been no three-dimensional structural data available for agnoprotein due to difficulties associated with the dynamic conversion from monomers to oligomers. Here, we report the first nuclear magnetic resonance (NMR) structure of a synthetic agnoprotein peptide spanning amino acids Thr17 to Glu55 where Lys23 to Phe39 encompassing the Leu/Ile/Phe-rich domain forms an amphipathic α-helix. On the basis of these structural data, a number of Ala substitution mutations were made to investigate the role of the α-helix in the structure and function of agnoprotein. Single L29A and L36A mutations exhibited a significant negative effect on both protein stability and viral replication, whereas the L32A mutation did not. In addition, the L29A mutant displayed a highly nuclear localization pattern, in contrast to the pattern for the wild type (WT). Interestingly, a triple mutant, the L29A+L32A+L36A mutant, yielded no detectable agnoprotein expression, and the replication of this JCV mutant was significantly reduced, suggesting that Leu29 and Leu36 are located at the dimer interface, contributing to the structure and stability of agnoprotein. Two other single mutations, L33A and E34A, did not perturb agnoprotein stability as drastically as that observed with the L29A and L36A mutations, but they negatively affected viral replication, suggesting that the role of these residues is functional rather than structural. Thus, the agnoprotein dimerization domain can be targeted for the development of novel drugs active against JCV infection.Agnoprotein is a small regulatory protein of JC virus (JCV) and is required for the successful completion of the viral replication cycle. It forms highly stable dimers and oligomers through its hydrophobic (Leu/Ile/Phe-rich) domain, which has been shown to play essential roles in the stability and function of the protein. In this work, the Leu/Ile/Phe-rich domain has been further characterized by NMR studies using an agnoprotein peptide spanning amino acids T17 to Q54. Those studies revealed that the dimerization domain of the protein forms an amphipathic α-helix. Subsequent NMR structure-based mutational analysis of the region highlighted the critical importance of certain amino acids within the α-helix for the stability and function of agnoprotein. In conclusion, this study provides a solid foundation for developing effective therapeutic approaches against the dimerization domain of the protein to inhibit its critical roles in JCV infection.
|Hydrostatic pressure independently increases elastin and collagen co-expression in small-diameter engineered arterial constructs.|
Crapo PM, Wang Y
Journal of biomedical materials research Part A
Prior studies have demonstrated that smooth muscle cell (SMC) proliferation, migration, and extracellular matrix production increase with hydrostatic pressure in vitro. We have engineered highly compliant small-diameter arterial constructs by culturing primary adult baboon arterial SMCs under pulsatile perfusion on tubular, porous, elastomeric scaffolds composed of poly(glycerol sebacate) (PGS). This study investigates the effect of hydrostatic pressure on the biological and mechanical properties of PGS-based engineered arterial constructs. Pressure was raised using a downstream needle valve during perfusion while preserving flow rate and pulsatility, and constructs were evaluated by pressure-diameter testing and biochemical assays for collagen and elastin. Pressurized constructs contained half as much insoluble elastin as baboon common carotid arteries but were significantly less compliant, while constructs cultured at low hydrostatic pressure contained one-third as much insoluble elastin as baboon carotids and were similar in compliance. Hydrostatic pressure significantly increased construct burst pressure, collagen and insoluble elastin content, and soluble elastin concentration in culture medium. All arteries and constructs exhibited elastic recovery during pressure cycling. Hydrostatic pressure did not appear to affect radial distribution of SMCs, collagens I and III, and elastin. These results provide insights into the control of engineered smooth muscle tissue properties using hydrostatic pressure.Copyright © 2011 Wiley Periodicals, Inc.