The retroviral polyprotein Gag is the essential factor in a large number of viral pathogens, such as human immunodeficiency virus type 1 (HIV-1) and oncoviruses, that promotes the budding of progeny viral shells after binding to the host plasma membrane, leading to the formation of immature daughter particles which mature further into infectious viruses. A multitude of molecular interactions involved in membrane budding result in a complexity of the ensuing molecular reorganizations that impedes our understanding of these processes. This lack in understanding in turn prevents the targeting of this important step in the reproduction of virus particles with therapeutic interventions. Here, we focus on two hypotheses. (I) Gag binding to the lipid bilayer results from a hierarchical sequence of molecular interactions between the protein and the plasma membrane: Electrostatic steering of the membrane-binding domain, MA, to the bilayer surface; lipid-specific interaction of MA with the phosphatidylinositoldiphosphate PI(4,5)P2; and hydrophobic membrane insertion of a myristoyl anchor on MA's N-terminus. (II) In the full-length Gag polyprotein of HIV-1, the flexibility of the linker regions between distinct Gag domains is key for controlling the molecular reorganization that leads to membrane budding. We assembled a cross-disciplinary team of investigators who combine cutting-edge biophysical characterization capabilities of the structural and dynamic properties of proteins at membrane interfaces, located in Dr. Lashes' group at Carnegie Mellon University (CMU), with expertise in Gag protein expression, manipulation and characterization represented by Dr. Rein's group at the National Cancer Institute (NCI) which also has advanced capabilities in characterizing subcellular localization of protein constructs and the ultra- structural morphology of assembly products. These groups will work closely together to determine, in Aim 1, the factors that control the association of MA with membranes in binding studies, structural characterization with neutron scattering and quantitative measurements of the dynamics of protein association with lipid bilayers with correlation spectroscopy. With these tools, we also aim at understanding the mechanisms that lead to the recruitment of specific lipids into the viral shell.
Under Aim 2, we characterize the origin and the implications of the conformational reorganization of full-length Gag at membrane surfaces in experimental and computational studies. Our team of investigators with its complementing expertise is uniquely qualified to boost our understanding of the molecular processes involved in viral shell formation. The

Public Health Relevance

The multiplication of viruses such as HIV in infected cells depends on the association of a viral protein, Gag, with the cell's plasma membrane which is consumed to form new viral shells in a complex sequence of molecular reorganizations. In this research project, we will determine the overall process that leads to the formation of viral shells because a thorough understanding of this process will be valuable for the development of new therapeutic strategies for interfering with virus formation in infected cells.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-BST-M (50))
Program Officer
Sakalian, Michael
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
Carnegie-Mellon University
Schools of Arts and Sciences
United States
Zip Code
Nanda, Hirsh; GarcĂ­a Sakai, Victoria; Khodadadi, Sheila et al. (2018) Relaxation dynamics of saturated and unsaturated oriented lipid bilayers. Soft Matter 14:6119-6127
Dupuy, Fernando G; Pagano, Isabella; Andenoro, Kathryn et al. (2018) Selective Interaction of Colistin with Lipid Model Membranes. Biophys J 114:919-928
Zimmermann, Kerstin; Eells, Rebecca; Heinrich, Frank et al. (2017) The cytosolic domain of T-cell receptor ? associates with membranes in a dynamic equilibrium and deeply penetrates the bilayer. J Biol Chem 292:17746-17759
Eells, Rebecca; Barros, Marilia; Scott, Kerry M et al. (2017) Structural characterization of membrane-bound human immunodeficiency virus-1 Gag matrix with neutron reflectometry. Biointerphases 12:02D408
Barros, Marilia; Heinrich, Frank; Datta, Siddhartha A K et al. (2016) Membrane Binding of HIV-1 Matrix Protein: Dependence on Bilayer Composition and Protein Lipidation. J Virol 90:4544-4555
Shen, Yang; Barros, Marilia; Vennemann, Tarek et al. (2016) A bacteriophage endolysin that eliminates intracellular streptococci. Elife 5:
Dick, Robert A; Barros, Marilia; Jin, Danni et al. (2016) Membrane Binding of the Rous Sarcoma Virus Gag Protein Is Cooperative and Dependent on the Spacer Peptide Assembly Domain. J Virol 90:2473-85
O'Neil, Lauren; Andenoro, Kathryn; Pagano, Isabella et al. (2016) HIV-1 matrix-31 membrane binding peptide interacts differently with membranes containing PS vs. PI(4,5)P2. Biochim Biophys Acta 1858:3071-3081
Heinrich, Frank; Chakravarthy, Srinivas; Nanda, Hirsh et al. (2015) The PTEN Tumor Suppressor Forms Homodimers in Solution. Structure 23:1952-1957
Dick, Robert A; Datta, Siddhartha A K; Nanda, Hirsh et al. (2015) Hydrodynamic and Membrane Binding Properties of Purified Rous Sarcoma Virus Gag Protein. J Virol 89:10371-82

Showing the most recent 10 out of 19 publications