More Frequent Nonconservative Amino Acid Substitutions in the gp120 V3 Region in Patients with

Rapid CD4+ T Cell Decline Versus Patients with High CD4+ T Cell Variability

Kevin Paiz-Ramirez

Janelle N. Ruiz

Biology 398.01

Department of Biology

Loyola Marymount University

March 20, 2010

Outline

I. Entry of HIV-1 involves binding of gp120 to CD4 receptor and co-receptors

II. Are there structural differences in V3 region of HIV-1 gp120 between participants with rapid CD4+ T cell decline versus patients with high CD4+ T Cell variability?

III. Results: comparing our groupsI. Diversity and divergence of gp120 V3 region amino acid

sequences is higher in linear progresors versus high variability subjects

II. There are differences in secondary structure predictions between the two groups

III. Amino acid changes take place on the surface of gp120 and near the co-receptor binding site

IV. Post-translational modifications linear progressors occur near or on the co-receptor binding site

The Entry of HIV Involves Specific Interactions between gp120, CD4, and

the Co-receptor

• Kwong et al. (1998) solved the crystal structure of – gp120 (red)– CD4 (yellow) – An antibody that binds similarly

to the co-receptor (blue and aqua)

• Gp120 is crucial for fusion of HIV-1 to cell surface– Positioning – Timing

• CD4 binding induces conformational change in gp120

Structure of gp120 Core

Kwong, et, al 1998

Previous investigation revealed differences in diversity and divergence in

DNA sequence of gp120 V3 variants• Patients with high CD4 decline had greater diversity

and divergence in DNA sequence of gp120 V3 variants than patients with high variability in CD4 count

• Are there amino acid changes that lead to structural differences in gp120 between patients with a rapid CD4+ T cell decline versus patients with high CD4+ T Cell variability?

Linear Progressors High Variability

Differences in Amino Acid Sequences were observed between the Linear and

High Variability Groups

• Multiple sequence alignments based on amino acid sequences were generated for each subject using the clones from the first four visits

• Determined consensus sequence for each subject• Determined the sequence(s) with most differences

from consensus sequence for each subject

High Variability group has fewer differences between sequences and less divergence in

sequences

Subject 12

D

High Variability group has fewer differences between sequences and less divergence in sequences

Subject 8

High Variability group has fewer differences between sequences and less divergence in sequences

Subject 6

Linear Progressors had More Nonconservative Substitutions

Subject4

Linear Progressors had More Nonconservative Substitutions

Subject 10

Structure-Based Sequence Alignment of Core Gp120

Predicted Secondary Structures of the gp120 V3 Region shows six beta sheets

and one alpha helix

High Variability shows six beta sheets and one alpha helix

Subject 8 Subject 6

Subject 12

Linear Progressors show six beta sheets and one or two alpha helices

Subject 4 Subject 10

High Variability Participants had Amino Acid Substitutions Occur on the Protein Surface

Surface Surface

SurfaceBinding Site

Key: •Blue: Single, fully conserved residues•Green: Conservation of strong groups•Purple: Conservation of weak groups•Black: No consensus

Linear Progressor Participants Had a Greater Number of Nonconservative Amino Acid Substitutions Located on Binding Sites

Binding Site Binding Site

Binding Site Surface

Key: •Blue: Single, fully conserved residues•Green: Conservation of strong groups•Purple: Conservation of weak groups•Black: No consensus

Linear Progressor Participants Have Greater Major Amino Acid Changes on Protein

Binding Sites

Key: •Blue: Single, fully conserved residues•Green: Conservation of strong groups•Purple: Conservation of weak groups•Black: No consensus

Linear Progessor Participant Displaying Nonconservative Amino Acid Substitution Located on Binding Site

Sites of Post Translational Modification:Linear Progressors Have Slightly Greater Post Translational Modifications than High

Variability

The Linear Progressor group was different from the High Variability group on a number of

different measures

• Linear progressors – had greater number of amino acid sequence differences – greater amount of nonconserved amino acid substitutions – had greater number of major amino acid changes in CD4-binding

regions– showed greater post-translational modifications

• This could indicate greater structural differences in linear progressors

• Further studies could examine protein structural differences variants within gp41 region

Pancera et al. (2010) examined the region where gp120 interacts with gp41

• This region had not been explored by earlier studies (Kwong et al)

• gp120 elements proximal to gp41 completed a 7 stranded Beta sandwich

• Facilitated movement between outer domain and gp41

• Kwong et al. also observed a conformational change with the virus in the v3 region

• This corroborates with Pancera’s observed changes in the gp41

Conclusion

• Entry of HIV-1 involves the binding of gp120 to CD4 receptor and co-receptors

• There are structural differences in the V3 region of HIV-1 gp120 between participants with rapid CD4+ T cell decline and patients with high CD4+ T Cell variability

• The diversity and divergence of gp120 V3 region Amino Acid sequences is higer in linear progressors

• Presented differences in secondary structure between linear and high variability

• Amino acid changes take place on the surface of gp120 and near the co-receptor binding site

• Post-translational modifications linear progressors occur near or on the co-receptor binding site

• Pancera et al & Kwong et al observed conformational changes in the gp41 and V3 region

References

• Kwong PD, Wyatt R, Robinson J, Sweet RW, Sodroski J, and Hendrickson WA. Structure of glycoprotein in complex with the CD4 receptor and a neutralizing human antibody. Nature 1998 Jun 18; 398(6686) 648-59.

• Pancera M, Majeed S, Ban YE, Chen L, Huang CC, Kong L, Kown YD, Stuckey J, Zhou T, Robinson JE, Schief WR, Sodroski J, Wyatt R, and Kwong PD. Structure of HIV-1 gp120 with gp41-interactive region reveals layered envelope architecture and basis of conformational mobility. Proc Natl Acad Sci USA 2010 doi:10.1073