The story of TIM family proteins and the regulation of viral infection just gets more and more interesting. We’ve previously explored the role of TIM-1 in mediating Ebola and Marburg virus infection. We’ve now published our newest work on modulation of HIV cellular infection by TIM-1: http://www.pnas.org/content/early/2014/08/14/1404851111.abstract
In collaboration with Wendy Maury’s lab at the University of Iowa we have published a follow-up paper describing our work characterizing the functional domains of TIM-1 required for infection of cells by the Ebola and Marburg filoviruses. This work may one day lead to the development of therapeautics to stop or control Ebola outbreaks, such as the one occurring now in the West African country of Guinea. Congratulations to Sven Moller-Tank, Lorraine Albritton (University of Tenneesee) and Wendy Maury on this important work.
here is the link: http://jvi.asm.org/content/early/2014/03/27/JVI.00300-14.abstract
here is the abstract:
Characterizing functional domains for TIM-mediated enveloped virus entry.
Sven Moller-Tank, Lorraine M. Albritton, Paul D. Rennert and Wendy Maury*. Department of Microbiology, University of Iowa, Iowa City, Iowa, USA, Department of Microbiology, Immunology & Biochemistry, University of Tennessee Health Science Center, Memphis, Tennessee, US, SugarCone Biotech LLC, Holliston, Massachusetts, USA. Journal of Virology 2014. Published ahead of print 2 April 2014, doi: 10.1128/JVI.00300-14
T-cell immunoglobulin and mucin domain 1 (TIM-1) and other TIM family members were recently identified as phosphatidylserine (PtdSer)-mediated virus entry enhancing receptors (PVEERs). These proteins enhance entry of Ebola virus (EBOV) and other viruses by binding PtdSer on the viral envelope, concentrating virus on the cell surface, and promoting subsequent internalization. The PtdSer binding activity of the IgV domain is essential for both virus binding and internalization by TIM-1. However, TIM-3, whose IgV domain also binds PtdSer, does not effectively enhance virus entry indicating that other domains of TIM proteins are functionally important. Here, we investigate the domains supporting enhancement of enveloped virus entry, thereby defining the features necessary for a functional PVEER. Using a variety of chimeras and deletion mutants, we found that in addition to a functional PtdSer binding domain PVEERs require a stalk domain of sufficient length, containing sequences that promote an extended structure. Neither the cytoplasmic nor transmembrane domain of TIM-1 is essential for enhancing virus entry, provided the protein is still plasma membrane bound. Based on these defined characteristics, we generated a mimic lacking TIM sequences and composed of Annexin V, the mucin like domain of α-dystroglycan, and a glycophosphatidylinositol anchor that functioned as a PVEER to enhance transduction of virions displaying Ebola, Chikungunya, Ross River, or Sindbis virus glycoproteins. This identification of the key features necessary for PtdSer-mediated enhancement of virus entry provides a basis for more effective recognition of unknown PVEERs.
IMPORTANCE (nontechnical, 150 word limit): T-cell immunoglobulin and mucin domain 1 (TIM-1) and other TIM family members are recently identified phosphatidylserine (PtdSer)-mediated virus entry enhancing receptors (PVEERs). These proteins enhance virus entry by binding the phospholipid, PtdSer, present on the viral membrane. While it is known that the PtdSer binding is essential for the PVEER function of TIM-1, TIM-3 shares this binding activity but does not enhance virus entry. No comprehensive studies have been done to characterize the other domains of TIM-1. In this study, using a variety of chimeric proteins and deletion mutants, we define the features necessary for a functional PVEER. With these features in mind, we generated a TIM-1 mimic using functionally similar domains from other proteins. This mimic, like TIM-1, effectively enhanced transduction. These studies provide insight into the key features necessary for PVEERs and will allow for more effective identification of unknown PVEERs.