No abstract

The role and outcome of the muscarinic M2 acetylcholine receptor (M2R) signaling in healthy and diseased cardiomyocytes is still a matter of debate. Here, we report that the long isoform of the regulator of G protein signaling 3 (RGS3L) functions as a switch in the muscarinic signaling, most likely of the M2R, in primary cardiomyocytes. High levels of RGS3L, as found in heart failure, redirect the Gi-mediated Rac1 activation into a Gi-mediated RhoA/ROCK activation. Functionally, this switch resulted in a reduced production of reactive oxygen species (− 50%) in cardiomyocytes and an inotropic response (+ 18%) in transduced engineered heart tissues. Importantly, we could show that an adeno-associated virus 9-mediated overexpression of RGS3L in rats in vivo, increased the contractility of ventricular strips by maximally about twofold. Mechanistically, we demonstrate that this switch is mediated by a complex formation of RGS3L with the GTPase-activating protein p190RhoGAP, which balances the activity of RhoA and Rac1 by altering its substrate preference in cardiomyocytes. Enhancement of this complex formation could open new possibilities in the regulation of the contractility of the diseased heart.

Professor Susanne Lutz First and most importantly, I want to thank you, Susanne, for giving me the opportunity to work in your lab and for sharing your interest in science with me. Thank you for supporting my strengths and for helping me to work on my weaknesses. Thank you for your continuous support and for making it possible that this thesis has now been completed. Professor Ralf DresselThank you for being part of my thesis committee, for your calm and friendly way of support which always encouraged me to move forward. Thank you very much for valuable suggestions and your interest in my work. Professor Dörthe Katschinski Thank you so much that you jumped on board when, due to a tragic incident, I needed a new thesis committee member. Thank you for your seemingly endless positive energy, which kept me motivated until I finished this thesis. And of course, I am very grateful for the partial funding of my position which also allowed me to test my teaching skills in physiology. Professor Wolfram Zimmermann Thank you very much for the great working environment, for giving me the opportunity to work with a group of smart and friendly people and for the amazing technical equipment. I really enjoyed spending a lot of time with my friend the confocal microscope. The Lutz lab I would like to thank all the former and current members of the Lutz lab. Thanks to Christina Würtz and Christiane Vettel for the important preliminary work, which finally led to my project. Thanks to Beate Ramba and Kerstin Schenk for technical assistance, for their knowledge and guidance and for keeping the Lutz lab running. Particularly, I want to thank Anita and Feli for being great colleagues and friends. Thank you for your continuous interest in the progress of my thesis as well as for your kind words during tough times. Technical assistants in the Institute of Pharmacology and Toxicology Thank you so much for keeping all the labs running through your continuous work and regular admonitions, for ordering all the necessary consumables and for a lot of technical advice. SFB 1002 Service Unit Thank you very much for providing our group with TAC-operated mice and the respective echocardiography data. Thank you for your expertise and the great organization of all the surgeries. AcknowledgmentV My friends and running colleagues A big thank you to Henna, Andrea, Bene, Flo, Schmitzens, Julia, Ruwan, Jonas, Miriam, Daniel, Kathi and all the others who taught me that there is a life besides the lab and who make this life much funnier. Thanks to all the crazy running guys who helped me to clear my head after stressful days.My family Mutti, Jörg, thank you so much for always being there and for your support through good and hard times. It is the best feeling to know that you will be so proud when you read this thesis. There is only one person who might even be prouder. Gilbert, it is great to have a brother like you! Petra, Reinhart, I am so happy that we are one big family now. Thank you for all the time and support, which made it possible for me to fini...