Recruitment of both the ESCRT and autophagic machineries to ejecting Mycobacterium marinum

Abstract

Cytosolic Mycobacterium marinum are ejected from host cells such as macrophages or the amoeba Dictyostelium discoideum in a non‐lytic fashion. As described previously, the autophagic machinery is recruited to ejecting bacteria and supports host cell integrity during egress. Here, we show that the ESCRT machinery is also recruited to ejecting bacteria, partially dependent on an intact autophagic pathway. As such, the AAA‐ATPase Vps4 shows a distinct localization at the ejectosome structure in comparison to fluorescently tagged Vps32, Tsg101 and Alix. Along the bacterium engaged in ejection, ESCRT and the autophagic component Atg8 show partial colocalization. We hypothesize that both, the ESCRT and autophagic machinery localize to the bacterium as part of a membrane damage response, as well as part of a “frustrated autophagosome" that is unable to engulf the ejecting bacterium.

Mechanisms of host cell exit by intracellular pathogens

“…This membrane-dependent exit includes actin-driven membrane protrusions enabling the spread of single bacteria between cells, extrusions and budding of microbes packed in a membranous compartment as well as ejection, expulsion and exocytosis of free microbes. A study by Gerstenmaier et al (2023) investigates the machinery of Mycobacterium ejection as an example of membranedependent exit.…”