Role of magnesium and a phagosomal P-type ATPase in intracellular bacterial killing

Abstract

SummaryBacterial ingestion and killing by phagocytic cells are essential processes to protect the human body from infectious microorganisms. However, only few proteins implicated in intracellular bacterial killing have been identified to date. We used Dictyostelium discoideum, a phagocytic bacterial predator, to study intracellular killing. In a random genetic screen we identified Kil2, a type V P-ATPase as an essential element for efficient intracellular killing of Klebsiella pneumoniae bacteria. Interestingly, kil2 knockout cells still killed efficiently several other species of bacteria, and did not show enhanced susceptibility to Mycobacterium marinum intracellular replication. Kil2 is present in the phagosomal membrane, and its structure suggests that it pumps cations into the phagosomal lumen. The killing defect of kil2 knockout cells was rescued by the addition of magnesium ions, suggesting that Kil2 may function as a magnesium pump. In agreement with this, kil2 mutant cells exhibited a specific defect for growth at high concentrations of magnesium. Phagosomal protease activity was lower in kil2 mutant cells than in wild-type cells, a phenotype reversed by the addition of magnesium to the medium. Kil2 may act as a magnesium pump maintaining magnesium concentration in phagosomes, thus ensuring optimal activity of phagosomal proteases and efficient killing of bacteria.

Mucolipin controls lysosome exocytosis in Dictyostelium

“…2B). Mucolipin was detected at low levels in early phagosomes, but accumulated in later phagosomes -a profile that is similar to that of the p80 endosomal marker (Lelong et al, 2011). Together, these results indicate that mucolipin is largely present in post-lysosomes in Dictyostelium cells.…”

Cellular function and pathological role of ATP13A2 and related P-type transport ATPases in Parkinson's disease and other neurological disorders

“…The ATP13A2 homologue Kil2 in Dicytostelium discoideum , a phagocytic bacterial predator, is required for Mg 2+ -dependent killing of ingested Klebsiella (Lelong et al, 2011). Also the ATP13A2 homologue CATP-6 in C. elegans has been implicated in Mg 2+ uptake (Lambie et al, 2013).…”

Is Encephalopathy a Mechanism to Renew Sulfate in Autism?

“…In experiments on the amoeba, D. discoldeum, a mutant with a defective form of the protein kil2 exhibited an impaired ability to break down proteins in the cell walls of certain bacteria following phagocytosis [106]. The experiments demonstrated conclusively that kil2 enables magnesium to be pumped into the lysosome, and that this magnesium enrichment is essential for the proper function of a protease that breaks down the bacterial cell walls.…”

“…A dangerous condition can arise when these nutrients are severely depleted, as it has been established that both magnesium and heparan sulfate play important roles in xenophagy, the processes in the phagolysosome leading to capture, killing and digestion of the invasive microbes [106]. As previously shown the zinc ion in eNOS may play a catalytic role in the synthesis of sulfate from eNOS [23].…”