Christine Groß

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C6: Effects of Tax and p8 proteins on cell-to-cell transmission of Human T-cell lymphotropic virus type 1 (HTLV-1)

Principal investigator
Andrea Kreß

Mentor
Mirko Kummer

Molecular mechanisms of cell-to-cell transmission of human T-lymphotropic virus type 1 (HTLV-1)

Human T-lymphotropic virus type 1 (HTLV-1) is a member of the delta-retroviruses and the causative agent of a severe neoplasm, adult T cell leukaemia/lymphoma (ATLL), and a neurodegenerative disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 preferentially infects activated CD4+ T-cells via cell-cell contacts, whereas cell-free virus transmission is very inefficient. Transmission of HTLV-1 depends on the "virological synapse" between an infected and an uninfected cell. In the infected cell the microtubule-organizing center (MTOC) is polarized towards the uninfected cell. This MTOC polarization is triggered by engagement of intercellular adhesion molecule 1 (ICAM-1) and by Tax, the oncoprotein of HTLV-1. Thus far, detailed molecular mechanisms of Tax-mediated virus transmission are unknown.
Our group found that Tax induces the protein Fascin that plays a role in cytoskeleton remodeling via binding to and bundling of actin. During my Master's thesis I could show that Fascin accumulates and colocalizes with actin at cell-cell contacts in Tax-transfected and chronically HTLV-1-infected T-cells (see figure). Interestingly, the accumulation of both Fascin and actin at cell-cell-contacts was reverted in the presence of Fascin-specific shRNAs. In transmission assays, we found that repression of Fascin in HTLV-1-infected cells led to reduced transactivation of co-cultured reporter T-cells. Inhibition of the actin and tubulin cytoskeleton caused less release of the HTLV-1 core protein gag p19 into the supernatant of the cell culture, whereas repression of Fascin via shRNA led to higher levels of released gag p19. Thus, the concentration of cell-free viruses rose in the absence of Fascin, underlining the idea that Fascin could be involved in virus transmission. The centre of our current research is to examine the role of Fascin in virus transmission in more detail. Moreover, we want to identify novel pathways guided by Tax that are required for HTLV-1 transmission. As Tax alters the expression of cell adhesion and surface molecules and components of the cytoskeleton, we plan to systematically knock down cellular Tax targets and study their impact on HTLV-1 transmission.

 

Figure: Fascin and actin colocalize at cell-cell contacts in HTLV-1-infected MT-2 cells. (A) Immunofluorescence staining of actin (red, b) and Fascin (turquoise, c) as well as the overlay of the single fluorescences (d) in HTLV-1 infected MT-2 cells. Phase contrast (e) and staining of the nucleus (DAPI, blue, a) served as controls. Knockdown of Fascin (shFascin5) and the internal shRNA control (shNonsense) were compared to untreated MT-2 cells. (B) Analysis of the cell contact via an arbitrary region of interest (ROI). The intensities of actin (red) and Fascin (turquoise) specific fluorescences and of DAPI (blue) were determined and plotted against the length of the ROI.

 

Publications

Wiesmann V, Gross C, Franz D, Thoma-Kress AK, Wittenberg T. (2016). Combining Active Contours and Active Shapes for Segmentation of Fluorescently Stained Cells. Bildverarbeitung fuer die Medizin 2016. Springer Berlin Heidelberg, 2016. 122-127.

Gross C, Thoma-Kress AK. (2016). Molecular Mechanisms of HTLV-1 Cell-to-Cell Transmission. Viruses 2016, 8, 74; doi:10.3390/v8030074.

Mohr CF, Kalmer M, Gross C, Mann MC, Sterz KR, Kieser A, Fleckenstein B, Kress AK. (2014). The tumor marker Fascin is induced by the EBV-encoded oncoprotein LMP1 via NF-kappaB signals in lymphocytes and contributes to their invasive migration. Cell Commun Signal. 12(1):46

Mohr CF, Gross C, Bros M, Reske-Kunz AB, Biesinger B, Thoma-Kress AK. (2015). Regulation of the tumor marker Fascin by the viral oncoprotein Tax of human T-cell leukemia virus type 1 (HTLV-1) depends on promoter activation and on a promoter-independent mechanism. Virology. 2015 Sep 9;485:481-491

 

Presentations

October 2016 8th Annual Retreat, Erlangen School of Molecular Communication, Schloss Schney, Lichtenfels, Germany
”The actin-bundling protein Fascin augments transmission of Human T-cell leukemia virus type 1 (HTLV-1)”
Poster
     
October 2015 2nd International SFB 796 Conference: Mechanisms of microbial host cell manipulation: From plants to humans, Erlangen, Germany
”The Tax-inducible actin-bundling protein Fascin is required for release and cell-to-cell transmission of Human T-cell leukemia virus type 1 (HTLV-1)”
Poster
     
July 2015 7th Annual Retreat, Erlangen School of Molecular Communication, Schloss Hirschberg, Beilngries, Germany
”FASCINating HTLV-1 transmission - Searching for the mechanism”
Talk
     
March 2015

25rd Annual Meeting of the Society for Virology, Bochum, Germany
“The actin-bundling protein Fascin enhances HTLV-1 release and cell-to-cell transmission”

Talk
     
March 2015 25rd Annual Meeting of the Society for Virology, Bochum, Germany “COL4A1 and COL4A2 as novel Tax targets with a possible role in biofilm formation and HTLV-1 transmission”
Poster
     
September 2014

Actin Dynamics Summer School 2014, Regensburg, Germany
“The actin-bundling protein Fascin contributes to efficient cell-to-cell transmission of Human T-cell leukemia virus type 1 (HTLV-1)”

Talk
     
July 2014 6th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
“Assessing the role of Fascin and COL4A1/2 in HTLV-1 transmission”
Talk
     
September 2013 5th European Congress of Virology 2013, Lyon, France
Influence of the actin bundling protein Fascin on HTLV 1 transmission
Poster
     
July 2013 5th Annual Retreat, Erlangen School of Molecular Communication, Kloster Banz, Bad Staffelstein, Germany
Molecular mechanisms of cell-to-cell transmission of human T-lymphotropic virus type 1 (HTLV-1)
Talk
     
March 2013 23rd Annual Meeting of the Society for Virology, Kiel, Germany
Contribution of the actin-bundling protein Fascin to HTLV-1 transmission
Poster