Abstract
Bacterial pathogen Legionella pneumophila is the causative agent of Legionnaires' disease, which is associated with intracellular replication of the bacteria in macrophages of human innate immune system. Recent studies indicate that pathogenic bacteria can subvert host cell phosphoinositide (PI) metabolism by translocated virulence effectors. However, in which manner Legionella actively exploits PI lipids to benefit its infection is not well characterized. Here we report that L. pneumophila encodes an effector protein, named SidP, that functions as a PI-3-phosphatase specifically hydrolyzing PI(3)P and PI(3,5)P2 in vitro. This activity of SidP rescues the growth phenotype of a yeast strain defective in PI(3)P phosphatase activity. Crystal structure of SidP orthologue from Legionella longbeachae reveals that this unique PI-3-phosphatase is composed of three distinct domains: a large catalytic domain, an appendage domain that is inserted into the N-terminal portion of the catalytic domain, and a C-terminal α-helical domain. SidP has a small catalytic pocket that presumably provides substrate specificity by limiting the accessibility of bulky PIs with multiple phosphate groups. Together, our identification of a unique family of Legionella PI phosphatases highlights a common scheme of exploiting host PI lipids in many intracellular bacterial pathogen infections.
Highlights
Controlling host phosphoinositide metabolism is critical in bacterial infection
Crystal structure of SidP orthologue from Legionella longbeachae reveals that this unique PI-3-phosphatase is composed of three distinct domains: a large catalytic domain, an appendage domain that is inserted into the N-terminal portion of the catalytic domain, and a C-terminal ␣-helical domain
We reported that the Legionella effector SidF is a bona fide PI phosphatase that hydrolyzes PI[3,4]P2 and PI[3,4,5]P3 at the D3 position [24]
Summary
Controlling host phosphoinositide metabolism is critical in bacterial infection. Results: A Legionella effector, SidP, has been identified as a phosphoinositide phosphatase, and its crystal structure was determined. Bacterial pathogen Legionella pneumophila is the causative agent of Legionnaires’ disease, which is associated with intracellular replication of the bacteria in macrophages of human innate immune system. We report that L. pneumophila encodes an effector protein, named SidP, that functions as a PI-3-phosphatase hydrolyzing PI[3]P and PI[3,5]P2 in vitro. Our identification of a unique family of Legionella PI phosphatases highlights a common scheme of exploiting host PI lipids in many intracellular bacterial pathogen infections. Our new findings of SidP as a PI phosphatase together with our previously reported results on SidF [24] strongly support that L. pneumophila actively exploits host PI metabolism via its own PI phosphatases during infection
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