Analyzing filamin C homeostasis

• Applicant: Professor Dr. Jörg Höhfeld
• Subject Area: Cell Biology
• Term: from 2010 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 148688621

• Final Report Year: 2019

Final Report Abstract

In the frame of the research unit we were able to establish fundamental principles of protein homeostasis (proteostasis) in muscle cells. The cochaperone BAG3 was identified as a central proteostasis factor, which balances transcription, translation and autophagy to maintain the proteome under mechanical stress. Its WW domain enables the cochaperone to contact diverse partner proteins during autophagosome formation and the regulation of transcription and translation, including the cytoskeleton protein SYNPO2/myopodin, components of the Hippo signalling cascade and regulators of the mTOR kinase. An initial trigger for the induction of BAG3-mediated proteostasis is the mechanical unfolding of the actin-crosslinking protein filamin C (FLNC) followed by cooperative binding of the diverse components of the BAG3 chaperone machinery to a mechanosensitive region of FLNC. We mapped the chaperone and cochaperone binding sites within this region and obtained evidence for a key function of the small heat shock protein HSPB8 in sensing FLNC unfolding. Finally, the biochemical characterization of the BAG3-P209L mutant variant provided insights into molecular aspects underlying BAG3-related muscle weaknesses. Biochemical experiments showed that the mutant protein retains the ability to interact with partner proteins and with its client filamin. However, it displays a conformational instability. These findings suggest that BAG3-P209L aggregation is accompanied by the sequestration of other essential proteostasis factor, which would explain the catastrophic collapse of protein homeostasis in diseased muscles.

Publications

• Chaperone-assisted selective autophagy is essential for muscle maintenance. Curr Biol 2010; 20: 143-148
  Arndt, Verena; Dick, Nikolaus; Tawo, Riga; Dreiseidler, Michael; Wenzel, Daniela; Hesse, Michael; Fürst, Dieter O.; Saftig, Paul; Saint, Robert; Fleischmann, Bernd K.; Hoch, Michael & Höhfeld, Jörg
  
• Pathophysiology of protein aggregation and extended phenotyping in filaminopathy. Brain 2012; 135: 2642-60
  Kley, Rudolf A.; Serdaroglu-Oflazer, Piraye; Leber, Yvonne; Odgerel, Zagaa; van der Ven, Peter F. M.; Olivé, Montse; Ferrer, Isidro; Onipe, Adekunle; Mihaylov, Mariya; Bilbao, Juan M.; Lee, Hee S.; Höhfeld, Jörg; Djinović-Carugo, Kristina; Kong, Kester; Tegenthoff, Martin; Peters, Sören A.; Stenzel, Werner; Vorgerd, Matthias; Goldfarb, Lev G.; ... & Fürst, Dieter O.
  
• Cellular mechanotransduction relies on tension-induced and chaperone-assisted autophagy. Curr Biol 2013; 23: 430-435
  Ulbricht, Anna; Eppler, Felix J.; Tapia, Victor E.; van der Ven, Peter F.M.; Hampe, Nico; Hersch, Nils; Vakeel, Padmanabhan; Stadel, Daniela; Haas, Albert; Saftig, Paul; Behrends, Christian; Fürst, Dieter O.; Volkmer, Rudolf; Hoffmann, Bernd; Kolanus, Waldemar & Höhfeld, Jörg
  
• Tension-induced autophagy: may the chaperone be with you. Autophagy 2013; 9: 920-922
  Ulbricht, Anna & Höhfeld, Jörg
  
• Induction and adaptation of chaperone-assisted selective autophagy CASA in response to resistance exercise in human skeletal muscle. Autophagy 2015; 11: 538-546
  Ulbricht, Anna; Gehlert, Sebastian; Leciejewski, Barbara; Schiffer, Thorsten; Bloch, Wilhelm & Höhfeld, Jörg
  
• BAG3-mediated proteostasis at a glance. J Cell Sci 2017; 130: 2781-2788
  Klimek, Christina; Kathage, Barbara; Wördehoff, Judith & Höhfeld, Jörg
  
• The cochaperone BAG3 coordinates protein synthesis and autophagy under mechanical strain through spatial regulation of mTORC1. Biochim Biophys Acta - Mol Cell Res 2017; 1864: 62-75
  Kathage, Barbara; Gehlert, Sebastian; Ulbricht, Anna; Lüdecke, Laura; Tapia, Victor E.; Orfanos, Zacharias; Wenzel, Daniela; Bloch, Wilhelm; Volkmer, Rudolf; Fleischmann, Bernd K.; Fürst, Dieter O. & Höhfeld, Jörg