Beta-chemokine induction of activation protein-1 and cyclic AMP responsive element activation in human myeloid cells.

Chemokines effect leukocyte chemotaxis and activation through their binding to specific G proteincoupled receptors. Although early steps in chemokine signal transduction pathways have been characterized, there is relatively limited information available at the transcription factor level. To that end, we have examined the binding activity on activation protein-1 (AP-1) and cyclic AMP responsive element (CRE) target sequences in human THP-1 myeloid cells after treatment with the b-chemokine macrophage inflammatory protein (MIP-1a). MIP-1a induced both AP-1 and CRE activation. Although inhibition of protein kinase C blocked the AP-1 activity induced by this chemokine, there was no decrease in CRE activation in the presence of a protein kinase A inhibitor. Using kinase assays, it appeared that mitogen-activated protein kinase pathways were involved in CRE activation. In addition, HIV-1 infection of THP-1 cells resulted in constitutive activation of AP-1 and CRE elements but no further response to MIP-1a treatment. These results suggest that b-chemokines act via protein kinase C-dependent pathways and mitogenactivated protein kinase pathways to modulate the host transcriptional response in myeloid cells, and that this response is altered by HIV infection.