Stellenticket Freie Universität Berlin

Tight Junc­tions regu­late paracel­lu­lar per­mea­bi­lity for solu­tes and water in epi­the­lia and endo­the­lia and are essen­tial for tis­sue bar­ri­ers. On the one hand, tran­si­ent ope­ning of tight junc­tions could improve drug deli­very across tis­sue bar­ri­ers, e.g. the intes­ti­nal epi­the­lium or the blood brain bar­rier. On the other hand, sta­bi­li­za­tion of patho­lo­gi­cally alte­red tight junc­tions could reco­ver the pro­tec­tive func­tion of a com­pro­mi­sed tis­sue bar­rier (e.g. in inflammatory bowel disease). To achieve this, the trans­mem­brane clau­din pro­te­ins are pro­mi­sing tar­gets, since they form the back­bone of tight junc­tions and deter­mine their paracel­lu­lar bar­rier pro­per­ties.

In the pro­ject, clau­din struc­ture-func­tion rela­ti­ons­hips will be cha­rac­te­ri­zed to elu­ci­date the mole­cu­lar mecha­nism of paracel­lu­lar per­mea­bi­lity regu­la­tion by claudins. Aim is, in par­ti­cu­lar, to cla­rify the mole­cu­lar archi­tec­ture of tight junc­tions and how claudins inter­act with each other at cell-cell con­tacts to form intra­mem­bra­nous poly­mers which – in a clau­din sub­typ-depen­dent man­ner – eit­her tigh­ten the paracel­lu­lar gap or form size- and charge-selec­tive chan­nels.

The fol­lo­wing methods will be app­lied: (a) struc­tu­ral bio­in­for­ma­tics: homo­logy mode­ling of clau­din pro­tein struc­tures, oli­go­mer docking and espe­ci­ally mole­cu­lar dyna­mics simu­la­ti­ons of mem­brane-embed­ded clau­din oli­go­mers; (b) expe­ri­men­tal: cell cul­ture, trans­fec­tion, cel­lu­lar recon­sti­tu­tion von tigh junc­tion strands/poly­mers, con­fo­cal and STED super reso­lu­tion micro­scopy, live cell ima­ging, FRET, FRAP, site-direc­ted muta­ge­ne­sis, freeze-frac­ture elec­tron micro­scopy, Wes­tern blot, che­mi­cal pro­tein cross­lin­king, mea­su­rement of paracel­lu­lar ion- and tracer per­mea­bi­lity

Very good Mas­ter degree in bio­che­mi­stry, bio­in­for­ma­tics, bio­logy, bio­phy­sics, bio­tech­no­logy or rela­ted field of study and strong inte­rest in struc­tu­ral and func­tio­nal cell bio­logy. Expe­ri­ence in struc­tu­ral bio­in­for­ma­tics or bio­che­mi­cal/cell bio­lo­gi­cal struc­ture-func­tion stu­dies is of advan­tage.

We offer a strong, com­mit­ted and enthu­si­astic sci­en­ti­fic envi­ron­ment at the inter­face bet­ween basic and pre­cli­ni­cal rese­arch. Optio­nal: Asso­cia­tion with DFG Rese­arch Trai­ning Group "TJ-Train", GRK 2318 (http://klinphys.charite.de/grk).

For app­li­ca­tion (please via email) and fur­ther infor­ma­tion please con­tact: Priv.-Doz. Dr. Jörg Piontek phone 030/450-514535, e-mail: joerg.piontek@charite.de, Insti­tut für Kli­ni­sche Phy­sio­lo­gie, Cha­rité, Hin­den­burg­damm 30, 12203 Ber­lin. For more Infor­ma­tion, see https://klinphys.charite.de and pro­ject-rela­ted publi­ca­ti­ons:
1. Hem­pel et al., 2020. Assem­bly of Tight Junc­tion Strands: Clau­din-10b and Clau­din-3 Form Homo Tetrame­ric Buil­ding Blocks that Poly­me­rise in a Chan­nel-Inde­pen­dent Man­ner. J Mol Biol. pii: S0022-2836(20)30222-9. doi: 10.1016/j.jmb.2020.02.034
2. Piontek et el., 2020. Mole­cu­lar archi­tec­ture and assem­bly of the tight junc­tion back­bone. Bio­chim Bio­phys Acta., 1862(7):183279. doi: 10.1016/j.bbamem.2020
3. Rosen­thal et al., 2019. Clau­din-15 forms a water chan­nel through the tight junc­tion with dis­tinct func­tion com­pa­red to clau­din-2. Acta Phy­siol (Oxf). 228(1):e13334. doi: 10.1111/apha.13334
4. Neu­haus et al., 2018. Rever­si­ble ope­ning of the blood-brain bar­rier by clau­din-5-bin­ding vari­ants of Clos­tri­dium per­frin­gens entero­to­xin's clau­din-bin­ding domain. Bio­ma­te­ri­als 161: 129-143
5. Klar et al. , 2017. Paracel­lu­lar cation per­mea­bi­lity due to a rare CLDN10B vari­ant cau­ses anhi­dro­sis and kid­ney damage. PLoS Genet;13(7):e1006897.doi: 10.1371/jour­nal.pgen.1006897
6. Milatz S et al., 2015. Pro­bing the cis-arran­ge­ment of pro­to­type tight junc­tion pro­te­ins clau­din-1 and clau­din-3. Bio­chem. J. 468(3): 449-458
7. Piontek et al., 2008. For­ma­tion of tight junc­tion: deter­mi­nants of homo­phi­lic inter­ac­tion bet­ween clas­sic claudins. FASEB J. 22:146-158