| Popis: |
In human monocyte-derived macrophages (MDM), the human immunodeficiency virus type 1 (HIV-1) assembles on deeply invaginated domains of the plasma membrane, or Intracellular Plasma Membrane-Connected Compartments (IPMC). Some of the membranes forming the IPMCs are decorated with thick, electron-dense, cytoplasmic coats. A range of proteins typically found in focal adhesion complexes (FAC) cluster at these coat structures. I show that the FAC protein CD18 co-localises with IPMCs in MDMs and primary alveolar macrophages. Upregulation of CD18 during macrophage differentiation coincides with the appearance of IPMCs, and downregulation of CD18 by RNAi perturbs the integrity of IPMCs in uninfected and HIV-infected MDMs. These observations suggest that CD18 and FACs are necessary to form, or maintain, IPMCs in MDMs. Bst-2/Tetherin inhibits the release of HIV by physically linking budding virions to the plasma membrane of host cells. The HIV-1 protein Vpu counteracts Tetherin, thus permitting HIV propagation. I show that type 1 interferons induce Tetherin expression in primary MDMs by around one order of magnitude. Tetherin localises to the cell surface, the trans-Golgi network, and IPMCs. Vpu downregulates Tetherin from the plasma membrane, and, in the absence of Vpu, HIV is retained in IPMCs. My data indicate that so-called virological synapses play a major role in the direct cell-cell transmission of HIV from macrophages to CD4+ T cells, and that Tetherin inhibits this intercellular spread. Thus, I show that Tetherin restricts HIV propagation from primary human macrophages regardless of the mode of transmission. Overall this study identifies structural components crucial for the integrity of the HIV assembly compartment, and characterises the Tetherin-mediated restriction of HIV in macrophages. |
