Receptor-mediated signaling in HTLV-1-infected lymphocytes
HTLV-1 is considered the etiologic agent of adult T cell leukemia and several chronic progressive immune-mediated diseases. While the pathogenesis is unclear, host mechanisms regulating viral replication are critical determinants. Since the HTLV-1 promoter contains sequences responsive to cAMP and P...
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| Format: | Dissertation |
| Language: | English |
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ProQuest Dissertations & Theses
01-01-1997
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| Online Access: | Get full text |
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| Summary: | HTLV-1 is considered the etiologic agent of adult T cell leukemia and several chronic progressive immune-mediated diseases. While the pathogenesis is unclear, host mechanisms regulating viral replication are critical determinants. Since the HTLV-1 promoter contains sequences responsive to cAMP and PKC, we hypothesized that signal transduction through the TCR/CD3 complex or CD2 receptor promotes viral replication in HTLV-1-infected lymphocytes. Pairs of mAbs directed against the CD2 receptor were mitogenic for resting PBMC, but inhibited ($\sp3$H) -thymidine incorporation 25-62% in CD2+ HTLV-1-infected lymphocytes. This was associated with a 20-40% reduction in cell number and viability, morphologic evidence of apoptosis and irreversible DNA fragmentation affecting 25-35% of CD2 stimulated cells. CD2 but not CD3 cross-linking concurrently increased viral p24 protein in cell supernatents 1.5-5.7 fold. Northern blot demonstrated a 2.5-4 fold increase in viral mRNA. Consistent with transcriptional regulation, reporter gene activity increased 30 fold in CD2-stimulated Jurkat cells co-transfected with tax and a luciferase reporter gene construct under control of the HTLV-1 promoter. While maximal reporter gene activity required expression of TRE sites in the HTLV-1 promoter, CD2 cross-linking also increased reporter gene activity in Jurkat cells co-transfected with tax and a promoter construct containing only the TATA box and downstream regulatory elements. Because TRE sites are homologous to cellular CREs, we hypothesized transcription depended on activation of cAMP. CD2 cross-linking increased cAMP four fold and was associated with an herbimycin A- and Rp-cAMP-sensitive increase in P-CREB. In contrast, CD3-mediated P-CREB was IL-2 dependent and not associated with induction of cAMP. Both CD2 and CD3 cross-linking increased binding of CREB to a $\sp{32}$P-CRE probe in the absence of exogenous IL-2. No change in DNA binding was observed with exogenous IL-2. These data suggest a possible physiologic mechanism whereby CD2-mediated cell adhesion and lymphocyte activation may promote viral transcription in infected lymphocytes. |
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| ISBN: | 0591513315 9780591513318 |