Identification of amino acid residues critical for the B cell growth-promoting activity of HIV-1 matrix protein p17 variants

Biochim Biophys Acta Gen Subj. 2019 Jan;1863(1):13-24. doi: 10.1016/j.bbagen.2018.09.016. Epub 2018 Sep 21.


Background: HIV-1 matrix protein p17 variants (vp17s) detected in HIV-1-infected patients with non-Hodgkin's lymphoma (HIV-NHL) display, differently from the wild-type protein (refp17), B cell growth-promoting activity. Biophysical analysis revealed that vp17s are destabilized as compared to refp17, motivating us to explore structure-function relationships.

Methods: We used: biophysical techniques (circular dichroism (CD), nuclear magnetic resonance (NMR) and thermal/GuHCL denaturation) to study protein conformation and stability; Surface plasmon resonance (SPR) to study interactions; Western blot to investigate signaling pathways; and Colony Formation and Soft Agar assays to study B cell proliferation and clonogenicity.

Results: By forcing the formation of a disulfide bridge between Cys residues at positions 57 and 87 we obtained a destabilized p17 capable of promoting B cell proliferation. This finding prompted us to dissect refp17 to identify the functional epitope. A synthetic peptide (F1) spanning from amino acid (aa) 2 to 21 was found to activate Akt and promote B cell proliferation and clonogenicity. Three positively charged aa (Arg15, Lys18 and Arg20) proved critical for sustaining the proliferative activity of both F1 and HIV-NHL-derived vp17s. Lack of any interaction of F1 with the known refp17 receptors suggests an alternate one involved in cell proliferation.

Conclusions: The molecular reasons for the proliferative activity of vp17s, compared to refp17, relies on the exposure of a functional epitope capable of activating Akt.

General significance: Our findings pave the way for identifying the receptor(s) responsible for B cell proliferation and offer new opportunities to identify novel treatment strategies in combating HIV-related NHL.

Keywords: B cell proliferation; HIV-1; Lymphoma; Matrix protein p17; p17 clonogenic epitope; p17 variants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • B-Lymphocytes / metabolism
  • B-Lymphocytes / virology*
  • Cell Adhesion
  • Cell Line, Tumor
  • Cell Proliferation
  • Cell Survival
  • Disulfides / chemistry
  • Epitopes / chemistry
  • HIV Antigens / chemistry*
  • HIV Infections / immunology*
  • HIV-1 / chemistry*
  • Humans
  • Light
  • Peptides / chemistry
  • Protein Conformation
  • Proto-Oncogene Proteins c-akt / metabolism
  • Recombinant Proteins / chemistry
  • Scattering, Radiation
  • Signal Transduction
  • Surface Plasmon Resonance
  • gag Gene Products, Human Immunodeficiency Virus / chemistry*


  • Disulfides
  • Epitopes
  • HIV Antigens
  • Peptides
  • Recombinant Proteins
  • gag Gene Products, Human Immunodeficiency Virus
  • p17 protein, Human Immunodeficiency Virus Type 1
  • AKT1 protein, human
  • Proto-Oncogene Proteins c-akt