The structure of Macrophage Expressed Gene-1, a phagolysosome immune effector that is activated upon acidification.

Pang, S. S.; Bayly-Jones, C.; Radjainia, M.; Spicer, B. A.; Law, R. H. P.; Hodel, A. W.; Ekkel, S. M.; Conroy, P. J.; Ramm, G.; Venugopal, H.; Bird, P. I.; Hoogenboom, B. W.; Voskoboinik, I.; Gambin, Y.; Sierecki, E.; Dunstone, M. A.; Whisstock, J. C.

doi:10.1101/580712

bioRxiv · 10.1101/580712

The structure of Macrophage Expressed Gene-1, a phagolysosome immune effector that is activated upon acidification.

Pang, S. S.·Bayly-Jones, C.·Radjainia, M.·Spicer, B. A.·Law, R. H. P.·Hodel, A. W.·Ekkel, S. M.·Conroy, P. J.·Ramm, G.·Venugopal, H.·Bird, P. I.·Hoogenboom, B. W.·Voskoboinik, I.·Gambin, Y.·Sierecki, E.·Dunstone, M. A.·Whisstock, J. C.

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Abstract

Macrophage Expressed Gene-1 (MPEG-1; also termed Perforin-2) is an endosomal / phagolysosomal perforin-like protein that is conserved across the metazoan kingdom and that functions within the phagolysosome to damage engulfed microbes. Like the Membrane Attack Complex and perforin, MPEG-1 has been postulated to form pores in target membranes, however, its mode of action remains to be established. We used single particle cryo-Electron Microscopy to determine the 2.4 [A] structure of a hexadecameric assembly of MPEG-1 that displays the expected features of a soluble pre-pore complex. We further discovered that the MPEG-1 pre-pore-like assemblies can be induced to perforate membranes through mild acidification, such as would occur within maturing phagolysosomes. We next solved the 3.6 [A] cryo-EM structure of MPEG-1 in complex with liposomes. Remarkably these data revealed that a C-terminal Multi-vesicular body of 12 kDa (MVB12)-associated {beta}-prism (MABP) domain interacts with target membranes in a mode that positions the pore forming machinery of MPEG-1 to point away from the bound membrane. This unexpected mechanism of membrane interaction raises the intriguing possibility that MPEG-1 may be able to remain bound to the phagolysosome membrane while simultaneously forming pores in engulfed bacterial targets.

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Pang, S. S., Bayly-Jones, C., Radjainia, M., Spicer, B. A., Law, R. H. P., Hodel, A. W., Ekkel, S. M., Conroy, P. J., Ramm, G., Venugopal, H., Bird, P. I., Hoogenboom, B. W., Voskoboinik, I., Gambin, Y., Sierecki, E., Dunstone, M. A., Whisstock, J. C.. 2019-03-17. The structure of Macrophage Expressed Gene-1, a phagolysosome immune effector that is activated upon acidification.. https://doi.org/10.1101/580712

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