CeMM: How immune cells kill bacteria with acid

Crucial protein for acidification of macrophage phagosome discovered

The first line of immune defense against invading pathogens like bacteria are macrophages, immune cells that engulf every foreign object that crosses their way and kill it with acid, in a process called phagocytosis. In their quest to systematically study proteins that transport chemicals across cellular membranes, researchers at CeMM characterized the critical role for transporter SLC4A7 in this process, providing valuable new insights for many pathologic conditions from inflammation to cancer. Their results were published in Cell Host & Microbe.

Among the many different kinds of immune cells that patrol the body, macrophages are the first when it comes to fight against a foreign threat. With their flexible and versatile surface, they engulf every microorganism or particle that could be harmful for the health of the organism, and enclose it in an intracellular membrane vesicle called phagosome. To eliminate the threat and break it down to its constituents, the interior of the phagosome needs to be effectively and progressively acidified. For this crucial part of phagocytosis, the macrophages must undergo multiple metabolic changes, which are not yet entirely understood.

The team of Giulio Superti-Furga, Scientific Director of CeMM, in collaboration with the laboratory of Nicolas Demaurex of the University of Geneva, discovered in their latest study that a membrane protein belonging to the family of “solute carriers” (SLCs) plays an essential role in phagocytosis and phagosome acidification. Their work was published in the journal Cell Host & Microbe (DOI 10.1016/j.chom.2018.04.013).

The researchers developed an essay with special cells in which they impaired the 391 human SLC genes individually using CRISPR/Cas9 gene editing technology. Strikingly, among all SLCs, SLC4A7, a sodium bicarbonate transporter, was the only one who turned out to be essential for macrophages to undergo phagocytosis and acidification. Cells with impaired SLC4A7 were unable to acidify their phagosomes and by consequence decreased their capacity to kill bacteria.

The results of this study do not only provide new fundamental insights into the molecular functioning of one of the most important cells of the immune system. As phagocytosis plays a significant role in various pathologic conditions from inflammation to cancer, these new insights are likely of relevance beyond the context of infectious diseases. The effort to understand the role of the different cellular transporters, supported by a grant of the European Research Council (ERC), has added a small new piece to the large and fascinating puzzle coupling trafficking of chemical matter to metabolism and cellular function.

Publication:

Vitaly Sedlyarov, Ruth Eichner, Enrico Girardi, Patrick Essletzbichler, Ulrich Goldmann, Paula Nunes-Hasler, Ismet Srndic, Anna Moskovskich, Leonhard X. Heinz, Felix Kartnig, Johannes W. Bigenzahn, Manuele Rebsamen, Pavel Kovarik, Nicolas Demaurex, and Giulio Superti-Furga. The Bicarbonate Transporter SLC4A7 Plays a Key Role in Macrophage Phagosome Acidification. Cell Host & Microbe, 2018. DOI: 10.1016/j.chom.2018.04.013

Funding:

The study was funded by the European Research Council (ERC), the Austrian Academy of Sciences, the Austrian Science Fund (FWF), the European Commission, and the European Molecular Biology Organization (EMBO).

About Giulio Superti-Furga

Giulio Superti-Furga Ph.D., is the Scientific Director of CeMM, the Research Center for Molecular Medicine of the Austrian Academy of Sciences, Professor for Medical Systems Biology at the Center for Physiology and Pharmacology of the Medical University of Vienna and Member of the Scientific Council of the European Research Council. As Scientific Director of CeMM, Giulio Superti-Furga has been fostering the precise and preventive medicine of the future by integrating basic research and clinical expertise to pursue pioneering diagnostic and therapeutic approaches. Among his major achievements to date are the elucidation of basic regulatory mechanisms of tyrosine kinases in human cancers, the determination of the precise mechanism of action of several drugs and the discovery of fundamental organization principles of the proteome and lipidome. In recent years, he has been focusing on membrane transporters, advocating the more systematic study of their function in the scientific community,
He is a member of the Austrian Academy of Sciences, the German Academy of Sciences Leopoldina, the European Molecular Biology Organization (EMBO), the European Academy of Cancer Sciences, and the Academia Europaea.
http://cemm.at/research/groups/giulio-superti-furga-group/

About CeMM

The mission of CeMM Research Center for Molecular Medicine of the Austrian Academy of Sciences is to achieve maximum scientific innovation in molecular medicine to improve healthcare. At CeMM, an international and creative team of scientists and medical doctors pursues free-minded basic life science research in a large and vibrant hospital environment of outstanding medical tradition and practice. CeMM’s research is based on post-genomic technologies and focuses on societally important diseases, such as immune disorders and infections, cancer and metabolic disorders. CeMM operates in a unique mode of super-cooperation, connecting biology with medicine, experiments with computation, discovery with translation, and science with society and the arts. The goal of CeMM is to pioneer the science that nurtures the precise, personalized, predictive and preventive medicine of the future. CeMM trains a modern blend of biomedical scientists and is located at the campus of the General Hospital and the Medical University of Vienna. www.cemm.at