Using WHIM syndrome-like cells to study hBD3 induced CXCR4 internalization

WHIM syndrome is a rare immunodeficiency disorder, characterized in part by disproportionate susceptibility of epithelial cells to human papillomavirus (HPV) induced warts. This susceptibility appears to be associated with a high degree of cellular activation caused by the inability of stromal derived factor 1 (SDF-1), the natural ligand of CXCR4, to promote internalization of the receptor. This, in turn, is due to defined mutations in the C-terminus of CXCR4. We previously showed that human beta defensin 3 (hBD3) can internalize CXCR4 without activating the cell (Feng et al, 2006). Objective: To determine the effect of hBD-3 on the internalization of CXCR4 truncation mutant, mimicking WHIM syndrome cells. Methods: CXCR4 was cloned into the pEGFP-N1 mammalian expression vector. CXCR4 mutant was then generated by site directed mutagenesis and verified by DNA sequencing. The CXCR4 mutant was subcloned into the pmCherry-N1 vector. pEGFP-N1-CXCR4 (green) and pmCherry-N1-CXCR4 mutant (red) were co-transfected into Hela cells. After 24 hours, the cells were put into serum free medium containing hBD-3 (20μg/ml), and images were captured. SDF-1 (30ng/ml) and PMA (100ng/ml) were used as positive controls. Results: Imaging data indicated that while the GFP tagged CXCR4 was internalized by hBD-3, the peptide was unable to induce internalization of the CXCR4 truncation mutant (pmCherry tagged). Conclusion: Results indicate that hBD3 dependent CXCR4 internalization requires an intact C-terminal tail; i.e., similar to SDF-1 dependent internalization. WHIM-like cells could be used to further study HPV related susceptibility and infection. Supported by NIH/NIDCR P01DE019759 (AW).