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Sugar-Binding Protein Facilitates HIV Cell Entry

A sugar-binding protein known as galectin-9 traps protein disulfide isomerase (PDI) on the surface of CD4 T-cells, making them more susceptible to HIV infection.

Interaction of glycoproteins (sugar-protein complexes) with other cell surface compounds known as lectins controls formation and maintenance of cell membranes and regulation of various cell functions.

Below is an edited excerpt from a press release issued by University of California at Los Angeles Health Sciences describing how one such protein, galectin-9, may influence susceptibility of T-cells to HIV entry.

Sugar-Binding Protein May Play a Role in HIV Infection

Specific types of "helper" T cells that are crucial to maintaining functioning immune systems contain an enzyme called PDI (protein disulfide isomerase). This enzyme affects how proteins fold into specific shapes, which in turn influences how the T cells behave. PDI also plays a role in HIV infection by helping to change the shape of the surface envelope protein of the virus, enabling the virus to interact optimally with receptors on the T cells, such as the CD4 molecule.

Though it is known that PDI inhibitors can prevent HIV infection, just how this happens has remained a mystery. And though it has been known that PDI, which normally lives inside the cell, can become entrapped on the cell's surface, it has not been understood how this happens.

Now, in a new study, UCLA researchers report that a sugar-binding protein called galectin-9 traps PDI on T-cells' surface, making them more susceptible to HIV infection.

The findings could lead researchers to a potential new target for anti-HIV therapeutics, such as therapies to inhibit PDI or galectin-9.

Investigator affiliations: Departments of Pathology & Laboratory Medicine and Microbiology, Immunology & Molecular Genetics, University of California School of Medicine, Los Angeles, CA.

6/21/11

Reference

S Bi, PW Hong, B Lee, and LG Baum. Galectin-9 binding to cell surface protein disulfide isomerase regulates the redox environment to enhance T-cell migration and HIV entry. Proceedings of the National Academy of Sciences (free full text). June 13, 2011 (Epub ahead of print).

Other Source

University of California at Los Angeles. Sugar-Binding Protein May Play a Role in HIV Infection. Press release. June 14, 2011.