Abstract
BackgroundDipeptidyl peptidase IV (DPPIV) also known as the T cell activation marker CD26 is a multifunctional protein which is involved in various biological processes. The association of human-DPPIV with components of the human immunodeficiency virus type-1 (HIV1) is well documented and raised some discussions. Several reports implicated the interaction of human-DPPIV with the HIV1 transcription transactivator protein (HIV1-Tat) and the inhibition of the dipeptidyl peptidase activity of DPPIV by the HIV1-Tat protein. Furthermore, enzyme kinetic data implied another binding site for the HIV1-Tat other than the active centre of DPPIV. However, the biological significance of this interaction of the HIV1-Tat protein and human-DPPIV has not been studied, yet. Therefore, we focused on the interaction of HIV1-Tat protein with DPPIV and investigated the subsequent biological consequences of this interaction in Spodoptera frugiperda cells, using the BAC-TO-BAC baculovirus system.ResultsThe HIV1-Tat protein (Tat-BRU) co-localized and co-immunoprecipitated with human-DPPIV protein, following co-expression in the baculovirus-driven Sf9 cell expression system. Furthermore, tyrosine phosphorylation of DPPIV protein was up-regulated in Tat/DPPIV-co-expressing cells after 72 h culturing and also in DPPIV-expressing Sf9 cells after application of purified recombinant Tat protein. As opposed to the expression of Tat alone, serine phosphorylation of the Tat protein was decreased when co-expressed with human-DPPIV protein.ConclusionsWe show for the first time that human-DPPIV and HIV1-Tat co-immunoprecipitate. Furthermore, our findings indicate that the interaction of HIV1-Tat and human-DPPIV may be involved in signalling platforms that regulate the biological function of both human-DPPIV and HIV1-Tat.
Highlights
Dipeptidyl peptidase IV (DPPIV) known as the T cell activation marker CD26 is a multifunctional protein which is involved in various biological processes
Human-DPPIV and human immunodeficiency virus type-1 (HIV1)-Tat co-associate in co-infected Sf9 cells To verify whether HIV1-Tat associates with humanDPPIV, Sf9 cells co-infected with Tat and DPPIV recombinant baculoviruses were harvested 48 h and 72 h post infection and stained with antibodies as described under methods
The DPPIV protein is predominantly located on the cell membrane
Summary
The HIV1-Tat protein (Tat-BRU) co-localized and co-immunoprecipitated with human-DPPIV protein, following co-expression in the baculovirus-driven Sf9 cell expression system. Tyrosine phosphorylation of DPPIV protein was up-regulated in Tat/DPPIV-co-expressing cells after 72 h culturing and in DPPIVexpressing Sf9 cells after application of purified recombinant Tat protein. As opposed to the expression of Tat alone, serine phosphorylation of the Tat protein was decreased when co-expressed with human-DPPIV protein
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