Secretory Leukocyte Protease Inhibitor Binds to Annexin II, a Cofactor for Macrophage HIV-1 Infection

Ma, Ge; Greenwell-Wild, Teresa; Lei, Kejian; Jin, Wenwen; Swisher, Jennifer; Hardegen, Neil; Wild, Carl T.; Wahl, Sharon M.

The detected binding between annexin II and rhSLPI was typically higher on differentiated macrophages than on freshly isolated blood monocytes or an undifferentiated monocytic cell line (Fig. 2 C, U937) , consistent with labeling studies and with PCR analysis (Fig. 3 A) of annexin II mRNA expression in these populations. Although annexin II protein was not detected in lysates of a T cell line (Fig. 2 C, Jurkat), it was evident in epithelial cell lysates (Fig. 2 C, A431) . Importantly, assessment of annexin II on CD4 Ï© blood mononuclear cells revealed differential membrane expression between freshly isolated resting CD4 Ï© T cells and CD14 Ï© monocytes (Fig. 3, B and C) . The absence of fluorescence staining of annexin II on CD4 Ï© T cells was confirmed by their lack of detectable annexin II membrane protein by Western blot (Fig. 3 D) . Collectively, these data identify mononuclear phagocytes as the predominant population expressing the SLPI membrane-binding protein, annexin II.