Biology subjects

Fricke, T.

Publications and source records attributed to Fricke, T..

3 recordsLinked to original sources

bioRxiv2023

Tim-1 and Tim-4 mediate entry of the human Kaposi's sarcoma-associated herpesvirus and the related rhesus monkey rhadinovirus

Kaposis sarcoma-associated herpesvirus (KSHV) is a human tumor virus. It is associated with Kaposis sarcoma, primary effusion lymphoma, and multicentric Castlemans disease. KSHV is known to interact with several different receptors, among them heparan sulfate proteoglycans, Eph family receptors, and integrins. We mutated the closely related rhesus monkey rhadinovirus in the known receptor interaction sites for Eph family and Plexin domain containing proteins and found it to still replicate on certain cells. This lytic virus was then used as a selection agent in a genome-wide CRISPR knockout screen, which identified TIM1 and NRP1 as host dependency factors. NRP1 is also host factor for the related Epstein-Barr virus and was recently reported to promote KSHV infection, which we confirm even if it functions with low efficiency on most cells and became functional only after ablation of the Eph receptor interaction. Further analysis through overexpression demonstrated that Tim-1 and the related Tim-4 are strong mediators of RRV and KSHV infection, in particular in the absence of other receptor interactions and even more pronounced for a KSHV mutant deleted in glycoprotein K8.1. Both Tim-1 and Tim-4 are heavily O-glycosylated phosphatidylserine (PS) receptors. For KSHV in particular, experiments with mutated Tim-1 and comparison to Ebola virus glycoprotein-driven entry indicate that the interaction with Tim-1 occurs through PS-binding by Tim-1 and suggest additional interaction in a PS-independent manner. The mucin-like domain of Tim-1 is required for optimal receptor function. The use of Tim proteins for entry is a novelty for herpesviruses and underscores the unique biology of KSHV and RRV.

microbiology↗

bioRxiv2019

EphA7 functions as a receptor for cell-to-cell transmission of Kaposi’s sarcoma-associated herpesvirus into BJAB B cells and for cell-free virus infection by the related rhesus monkey rhadinovirus

Kaposis sarcoma-associated herpesvirus (KSHV) is the causative agent of Kaposis sarcoma and is associated with two B cell malignancies, primary effusion lymphoma and the plasmablastic variant of multicentric Castlemans disease. EphA2 functions as a cellular receptor for the gH/gL glycoprotein complex of KSHV for several adherent cell types. KSHV gH/gL was previously shown to also weakly interact with other members of the Eph family of receptors. Whether these interactions are of functional consequence remained unclear so far, even if other A-type Ephs were shown to be able to compensate for absence of EphA2 in overexpression systems. Here, we demonstrate for the first time that endogenously expressed EphA7 in BJAB B cells is critical for the cell-to-cell transmission of KSHV from producer iSLK cells to BJAB target cells. The BJAB lymphoblastoid cell line often serves as a model for B cell infection and expresses only low levels of all Eph family receptors other than EphA7. Endogenous EphA7 could be precipitated from the cellular lysate of BJAB cells using recombinant gH/gL, and knockout of EphA7 significantly reduced transmission of KSHV into BJAB target cells by over 80%. Finally, we demonstrate that receptor function of EphA7 is conserved between cell-to-cell transmission of KSHV and cell-free infection by the related rhesus monkey rhadinovirus (RRV), which is relatively even more dependent on EphA7 for infection of BJAB cells.\n\nIMPORTANCEInfection of B cells is biologically relevant for two KSHV-associated malignancies, the plasmablastic variant of multicentric Castlemans disease (MCD) and primary effusion lymphoma (PEL). Elucidating the process of B cell infection is therefore important to understand the pathogenesis of these diseases. For various types of adherent cells, EphA2 has been shown by several groups to function as an entry receptor that is engaged by the gH/gL glycoprotein complex. Our previous findings indicate that KSHV does not only interact with EphA2, but can also bind to other members of the Eph family of receptor tyrosine kinases with comparatively lower avidity. We now analyzed the requirement of Eph interactions for infection of the BJAB B cell line, a model for infection of B cells by KSHV. We identify EphA7 as the principal Eph receptor for infection of this model B cell line by both KSHV and the related rhesus monkey rhadinovirus.

microbiology↗

bioRxiv2017

Targeted RNA knockdown by crRNA guided Csm in zebrafish

RNA interference (RNAi) is a powerful experimental tool for RNA knockdown, but not all organisms are amenable. Here, we provide a \"proof of principle\" demonstration that CRISPR endoribonucleases can be used for programmable mRNA transcript degradation. Using zebrafish as the animal model and Csm(crRNA) complexes as the CRISPR endoribonucleases, we have targeted a transgenic EGFP transcript expressed from a variety of promoters. A drastic decrease of fluorescence was achieved in germ cells of the vasa:EGFP line. Weaker effects were also seen in fish lines that express EGFP zygotically. Knockdown was statistically significant in cmcl2:EGFP and fli1:EGFP zebrafish lines at 1 day post fertilization (dpf), but reduced to background levels at 2 dpf. The nkx2.5:EGFP fish line was least susceptible to Csm mediated EGFP knockdown. We conclude that at the present stage, Csm mediated knockdown is already efficient for maternal transcripts, and may compare favorably with morpholinos for such targets in zebrafish.

genetics↗