ORIGINAL ARTICLE Selective protection of murine cerebral G i/o -proteins from inactivation by parenterally injected pertussis toxin Salvador Castaneda Vega 1,2 & Veronika Leiss 3 & Roland Piekorz 4 & Carsten Calaminus 1 & Katja Pexa 4 & Marta Vuozzo 1 & Andreas M. Schmid 1 & Vasudharani Devanathan 3,5 & Christian Kesenheimer 1 & Bernd J. Pichler 1,2 & Sandra Beer-Hammer 3 & Bernd Nürnberg 3,6 Received: 22 December 2018 /Revised: 30 October 2019 /Accepted: 12 November 2019 # Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Pertussis toxin (PTX) is a potent virulence factor in patients suffering from whooping cough, but in its detoxified version, it is applied for vaccination. It is thought to contribute to the pathology of the disease including various CNS malfunctions. Based on its enzymatic activity, PTX disrupts GPCR-dependent signaling by modifying the α-subunit of heterotrimeric G i/o -proteins. It is also extensively used as a research tool to study neuronal functions in vivo and in vitro. However, data demonstrating the penetration of PTX from the blood into the brain are missing. Here, we examined the Gα i/o -modifying activity of PTX in murine brains after its parenteral application. Ex vivo biodistribution analysis of [ 124 I]-PTX displayed poor distribution to the brain while relatively high concentrations were visible in the pancreas. PTX affected CNS and endocrine functions of the pancreas as shown by open-field and glucose tolerance tests, respectively. However, while pancreatic islet Gα i/o -proteins were modified, their neuronal counterparts in brain tissue were resistant towards PTX as indicated by different autoradiographic and immunoblot SDS-PAGE analyses. In contrast, PTX easily modified brain Gα i/o -proteins ex vivo. An attempt to increase BBB permeability by application of hypertonic mannitol did not show PTX activity on neuronal G proteins. Consistent with these findings, in vivo MRI analysis did not point to an increased blood-brain barrier (BBB) permeability following PTX treatment. Our data demon- strate that the CNS is protected from PTX. Thus, we hypothesize that the BBB hinders PTX to penetrate into the CNS and to deliver its enzymatic activity to brain Gα i/o -proteins. Key messages & i.p. applied PTX is poorly retained in the brain while reaches high concentration in the pancreas. & Pancreatic islet Gα i/o - but not cerebral Gα i/o -proteins are modified by i.p. administered PTX. & Gα i/o -proteins from isolated cerebral cell membranes were easily modified by PTX ex vivo. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00109-019-01854-1) contains supplementary material, which is available to authorized users. * Bernd Nürnberg bernd.nuernberg@uni-tuebingen.de 1 Werner Siemens Imaging Center, Department of Preclinical Imaging and Radiopharmacy, Eberhard Karls University Tübingen and University Medical Center, Tübingen, Germany 2 Department of Nuclear Medicine and Clinical Molecular Imaging, Eberhard Karls University, Tübingen, Germany 3 Department of Pharmacology and Experimental Therapy, Institute for Experimental and Clinical Pharmacology and Toxicology, Interfaculty Center for Pharmacogenomics and Drug Research, Eberhard Karls University Tübingen, 72074 Tübingen, Germany 4 Institute for Biochemistry and Molecular Biology II, Medical Faculty, Heinrich Heine University Düsseldorf, Düsseldorf, Germany 5 Neuroscience Lab, Department of Biology, Indian Institute of Science Education and Research (IISER), Tirupati, India 6 Department of Toxicology, Institute for Experimental and Clinical Pharmacology and Toxicology, Eberhard Karls University Tübingen, and University Medical Center, Tübingen, Germany Journal of Molecular Medicine https://doi.org/10.1007/s00109-019-01854-1