Universität zu Köln 

Prof. Dr. Thomas Benzing

Klinik II für Innere Medizin, Universitätsklinik Köln
CECAD Forschungszentrum
email: thomas.benzing@uk-koeln.de
phone: +49-(0)221 478 84441
?website

Mutations in the NPHS2 gene, which encodes the prohibitin homology (PHB-) domain protein Podocin, are the most common cause of hereditary nephrotic syndrome, a severe and progressive kidney disorder. We have shown that Podocin is part of a multiprotein complex that localises to the slit diaphragm, a specialised cell junction that connects adjacent processes of podocytes. Podocyte processes contain a highly dynamic contractile cytoskeleton; they interdigitate and closely enwrap the glomerular capillaries to contribute to the filtration barrier of the kidney. The closest homologue of Podocin in Caenorhabditis elegans is MEC-2. Podocin and MEC-2 are part of large multimolecular mechanosensitive membrane protein complexes. The formation and function of these megadalton ion channel complexes involves protein-protein interactions and lipid binding which is regulated through posttranslational modification of the auxiliary subunits of the channel complex. In this project we will address how phosphorylation and ubiquitylation of Podocin/MEC-2 and associated proteins influence the assembly and function of the Podocin/MEC-2 membrane protein supercomplexes. Our specific aims are to (1) characterise the role of phosphorylation of Podocin/MEC-2 in regulating assembly and function of the mechanosensitive channel complex using the MEC-2 touch receptor in C. elegans as an in vivo model, (2) establish a structure-function relationship between phosphorylation, lipid interaction, ubiquitylation and the formation of supercomplexes, (3) understand the contribution of ubiquitylation of Podocin/MEC-2 by HUWE1, a newly identified HECT domain ubiquitin ligase, for touch sensation in C. elegans and podocyte function in the mouse, and (4) transfer these findings to other membrane protein complexes consisting of similar components. It is expected that the results of this project will not only unravel important aspects in the regulation of mechanosensitive protein complexes but may also contribute to a better understanding of a clinically very important group of human disorders.

Running time: 01/2008 – 06/2015

Recent publications:

Völker, L.A., Petry, M., Abdelsabour-Khalaf, M., Schweizer, H., Yusuf, F., Busch, T., Schermer, B., Benzing, T., Brand-Saberi, B., Kretz, O., Höhne, M., and Kispert, A. (2012). Comparative analysis of Neph gene expression in mouse and chicken development. Histochem. Cell Biol. 137, 355-366.

Seeger-Nukpezah T., Liebau M.C., Höpker K., Lamkemeyer T., Benzing T., Golemis E.A., Schermer B. (2012). The centrosomal kinase plk1 localizes to the transition zone of primary cilia and induces phosphorylation of nephrocystin-1. PLoS One. ;7(6):e38838. Epub 2012 Jun 11.

Höhne M., Lorscheider, J., von Bardeleben, A., Dufner, M., Scharf, M.A., Godel, M., Helmstadter, M., Schurek, E.-M., Zank, S., Gerke, P., Kurschat, C., Sivritas, S.H., Neumann-Haefelin, E., Huber, T.B., Reinhardt, H.C., Schauss, A.C., Schermer, B., Fischbach, K.-F., and Benzing, T. (2011). The BAR Domain Protein PICK1 Regulates Cell Recognition and Morphogenesis by Interacting with Neph Proteins. Mol Cell Biol 31, 3241-3251. PubMed

Liebau, M.C., Höpker, K., Müller, R.U., Schmedding, I., Zank, S., Schairer, B., Fabretti, F., Höhne, M., Bartram, M-P., Dafinger, C., Hackl, M., Burst, V., Habbig, S., Zentgraf, H., Blaukat, A., Walz, G., Benzing, T., and Schermer, B. (2011). Nephrocystin-4 Regulates Pyk2-induced Tyrosine Phosphorylation of Nephrocystin-1 to Control Targeting to Monocilia. J Biol Chem 286, 14237-14245. PubMed

Schermer, B. and Benzing, T. (2009). Lipid-protein interactions along the slit diaphragm of podocytes. J. Am. Soc. Nephrol. 20, 473-478.

Hartleben, B., Schweizer, H., Lübben, P., Bartram, M.P., Möller, C.C., Herr, R., Wei, C., Neumann-Haefelin, E., Schermer, B., Zentgraf, H., Kerjaschki, D., Reiser, J., Walz, G., Benzing, T., and Huber, T.B. (2008). Neph-nephrin proteins bind the PAR3, PAR6, aPKC complex to regulate podocyte polarity. J. Biol. Chem. 283, 23033-23038.

Huber, T.B., Schermer, B., Müller, R.U., Höhne, M., Bartram, M., Calixto, A., Hagmann, H., Reinhardt, C., Koos, F., Kunzelmann, K., Shirokova, E., Krautwurst, D., Harteneck, D., Simons, M., Pavenstädt, H., Kerjaschki, D., Thiele, C., Walz, G., Chalfie, M., and Benzing, T. (2006). Podocin and MEC-2 bind cholesterol to regulate the activity of associated ion channels. Proc. Natl. Acad. Sci. U.S.A. 103, 17079-17086.

Benzing, T. (2004). Signaling at the slit diaphragm. J. Am. Soc. Nephrol. 15, 1382-1891.

Huber, T.B., Simons, M., Hartleben, B., Sernetz, L., Saleem, M., Schmidts, M., Gundlach, E., Walz, G., and Benzing, T. (2003). Molecular basis of the functional podocin-nephrin complex: mutations in the NPHS2 gene disrupt nephrin targeting to lipid raft microdomains. Hum. Mol. Genet. 12, 3397-3405.