The plasma membrane as a combat zone in the HIV battlefield

In the life of a cell, the plasma membrane fulfills a range of functions that go far beyond the shaping and maintenance of architectural features and the absorption of nutrients. The plasma membrane is a highly sophisticated structure whose phospholipidic backbone is loaded with proteins responsible for channeling the stream of information that continuously flows between a cell and its environment. Although the nucleus can intuitively be viewed as the cell's center of command, the translation of its genetic content is constantly modulated by signals triggered and often integrated at the level of the plasma membrane. Reciprocally, the cell exposes on or releases from its surface a wide variety of molecules that regulate its recognition by other cells and that sometimes influence the homeostasis of the whole organism.

The plasma membrane is also the site where intracellular pathogens first clash with their target and the place from which the immune system is subsequently called to the rescue. Correspondingly, the study of viruses has provided great strides in the comprehension of such fundamental processes as membrane fusion, protein transport, endocytosis, signal transduction, and antigen presentation, all phenomena that are intimately intertwined with the biology of membranes and their associated proteins. Recent progress in the analysis of the HIV, probably by now the most extensively characterized of all human pathogens, provides a good illustration of this paradigm. Just as the composition of the plasma membrane influences viral infectivity, the virus in turn uses components of the plasma membrane that are to its advantage and modifies others to suit its purposes. The interplay between HIV and the plasma membrane has much to offer in terms of understanding viral tropism and pathogenicity and normal cellular functions, and for developing new antiviral approaches.