Background: During early HIV-1 infection of CD4 T-lymphocytes, many host protein tyrosine kinases become activated within minutes, including phosphoprotein pp60 (c-Src) and the focal adhesion kinase family member, proline-rich tyrosine kinase 2 (Pyk2). Whether their activation facilitates or impedes infection remains to be determined.
Methods: c-Src kinase inhibitors (SU6656, PP1, and PP2), adenovectors [wild-type and dominant-negative (DN) c-src] or siRNA (targeting c-src or pyk2) were used to inhibit, compete with or knockdown c-Src in Jurkat C, Jurkat E6-1, Hut 78 or Kit225 T-cell lines. Cells were then infected with HIV-1 luciferase reporter virus expressing VSV-G or HXB2(X4) envelope, and luciferase activity was measured after 2 days. Reverse transcriptase activity and viral cDNA were measured 1 hour after infection, whereas integrated virus was measured 12 hours after infection.
Results: Pretreating Jurkat T-cells with SU6656 led to increased VSV-G luciferase activity. In the adenovector experiments, T-cells overexpressing dominant-negative c-Src, but not wild-type c-Src, showed increased luciferase activity after VSV-G infection. siRNA knockdown of c-Src or Pyk2, followed by HXB2 infection in Jurkat T-cells, lead to increased reverse transcriptase activity, viral cDNA, integrated virus, and increased luciferase activity.
Conclusions: Pyk2 is known to interact with c-Src. Thus, Pyk2 activation that coincides with increased c-Src activity during HIV-1 infection could be responsible for c-Src activation. Reduced c-Src activation increases HIV-1 reverse transcription, integration, and/or transcription, suggesting the high c-Src activity seen early in HIV-1 infection may be a cellular response to slow or prevent early infection in CD4 T-cells.