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Placenta. 2009 May;30(5):464-7. doi: 10.1016/j.placenta.2009.03.003. Epub 2009 Apr 1.

Cystatin B associates with signal transducer and activator of transcription 1 in monocyte-derived and placental macrophages.

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  • 1Department of Microbiology and Medical Zoology, University of Puerto Rico, San Juan, PR 00935.


Cystatin (CSTB, also known as stefin B), a cysteine protease inhibitor, recently was found to be down-regulated in the proteome of uninfected and HIV-1-infected placental macrophages (PMs) and associated with restricted HIV-1 replication in PM but not in monocyte-derived macrophages (MDMs). We investigated CSTB interactions with signal transducer and activator of transcription 1 (STAT-1) by immunoprecipitation studies because this molecule is known to activate HIV-1 replication. Since both CSTB and STAT-1 are related to HIV-1 replication, we hypothesized that these proteins could be interacting. We applied immunoprecipitation assays to determine STAT-1-CSTB interaction in uninfected and HIV-1-infected PM as compared with MDM. We found that CSTB associates with STAT-1 in PM and MDM. Further analyses indicated that the levels of STAT-1 tyrosine phosphorylation were higher in PM than MDM. High levels of tyrosine phosphorylation previously have been associated with HIV-1 inhibitory activity. This is the first report to demonstrate that cystatin B interacts with STAT-1 and that the levels of STAT-1 tyrosine phosphorylation (but not serine phosphorylation) between uninfected and HIV-infected PM and MDM are differentially regulated.

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