Charité Universitätsmedizin Berlin, Germany
Martha Sommer first became interested in the molecular mechanisms of signal transduction when studying bacterial chemotaxis at the University of Texas at Austin. Later she joined the lab of Prof. David Farrens at the Oregon Health & Science University, where she worked on the eukaryotic photoreceptor rhodopsin and its regulatory protein arrestin. After completing her Ph.D. in 2006, Dr. Sommer was awarded an International Research Fellowship from the National Science Foundation (USA) to continue her work on arrestin-rhodopsin interactions with the group of Prof. Klaus Peter Hofmann at the Charité Medical University in Berlin, Germany. Since 2013 Dr. Sommer has led her own research group within the Institute for Medical Physics and Biophysics at the Charité. Her research is focused on elucidating the molecular details of arrestin-receptor interactions, and ultimately how modulation of these interactions gives rise to complex cellular responses.
Nearly every physiological system in the animal organism is controlled in some part by G protein-coupled receptors (GPCRs). Arrestins bind to active, phosphorylated GPCRs to block G protein signalling, mediate receptor endocytosis, and stimulate arrestin-dependent signalling pathways. We recently discovered that arrestin can adopt different binding modes that entail different arrestin-to-receptor binding ratios (stoichiometry) and distinct arrestin conformations. This conformational repertoire is hypothesized to underlie the diverse ways in which arrestins regulate GPCRs. Although high resolution crystal structures are available for both activated GPCRs and pre-activated arrestins, our knowledge of the basic organization and structure of the arrestin-receptor complex is currently limited. We have tackled this problem using multiple biophysical methods applied to the GPCR rhodopsin and arrestin-1 from the retinal rod cell. We seek to elucidate the different receptor-binding modes of arrestin, both structurally and functionally, in order to understand why arrestin is such a versatile binding partner.
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