Abstract
The natural cysteine to serine variation at position 31 of Tat in HIV-1C disrupts the dicysteine motif attenuating the chemokine function of Tat. We ask if there exists a trade-off in terms of a gain of function for HIV-1C Tat due to this natural variation. We constructed two Tat-expression vectors encoding Tat proteins discordant for the serine 31 residue (CS-Tat vs. CC-Tat), expressed the proteins in Jurkat cells under doxycycline control, and performed the whole transcriptome analysis to compare the early events of Tat-induced host gene expression. Our analysis delineated a significant enrichment of pathways and gene ontologies associated with the angiogenic signaling events in CS-Tat stable cells. Subsequently, we validated and compared angiogenic signaling events induced by CS- vs. CC-Tat using human umbilical vein endothelial cells (HUVEC) and the human cerebral microvascular endothelial cell line (hCMEC/D3). CS-Tat significantly enhanced the production of CCL2 from HUVEC and induced an activated phenotype in endothelial cells conferring on them enhanced migration, invasion, and in vitro morphogenesis potential. The ability of CS-Tat to induce the activated phenotype in endothelial cells could be of significance, especially in the context of HIV-associated cardiovascular and neuronal disorders. The findings from the present study are likely to help appreciate the functional significance of the SAR (signature amino acid residues) influencing the unique biological properties.
Highlights
HIV-1 genetic subtypes differ from one another in several molecular and biological properties, including genetic sequence variation, co-receptor usage, pathogenicity, replication fitness, transmission, and geographical distribution [1, 2]
We induced reverse tetracyclinecontrolled transactivator 3 gene (rtTA3)-CC-Tat Jurkat cells using 800 ng/ml of doxycycline and RNA was isolated from the cells at 6-h time intervals to monitor the modulation in the expression of Tat and a few cytokines comprising of TNF-α, IL-8, and IL-10 (Supplementary Figure 2A)
The clones express the WT (CS) and CC-Tat proteins being similar in sequence activated several common signaling pathways, but dysregulated specific pathways differentially
Summary
HIV-1 genetic subtypes differ from one another in several molecular and biological properties, including genetic sequence variation, co-receptor usage, pathogenicity, replication fitness, transmission, and geographical distribution [1, 2]. While factors such as the demographic variations, founder effect, host factor landscape differences, and socioeconomic parameters could significantly influence and modulate the observed differences among the HIV-1 genetic subtypes, natural genetic variations unique for individual viral subtypes play critical roles [3]. The study of the signature amino acid residues may offer valuable leads underpinning the biological differences among genetic subtypes of HIV-1 or other viruses and the survival advantage that the viral strains may have acquired in a specific population. We used HIV-1 Tat as a model protein to understand the significance of S31, an important SAR of HIV-1C
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