Sphingomyelin Biosynthesis Is Essential for Phagocytic Signaling during Mycobacterium tuberculosis Host Cell Entry.

Phagocytosis by alveolar macrophages is the obligate first step in () infection, yet the mechanism underlying this process is incompletely understood. Here, we show that invasion relies on an intact sphingolipid biosynthetic pathway. Inhibition or knockout of early sphingolipid biosynthetic enzymes greatly reduces uptake across multiple phagocytic cell types without affecting other forms of endocytosis. While the phagocytic receptor dectin-1 undergoes normal clustering at the pathogen contact sites, sphingolipid biosynthetic mutant cells fail to segregate the regulatory phosphatase CD45 from the clustered receptors. Blocking sphingolipid production also impairs downstream activation of Rho GTPases, actin dynamics, and phosphoinositide turnover at the nascent phagocytic cup. Moreover, we found that production of sphingomyelin, not glycosphingolipids, is essential for uptake. Collectively, our data support a critical role of sphingomyelin biosynthesis in an early stage of infection and provide novel insights into the mechanism underlying phagocytic entry of this pathogen. () invades alveolar macrophages through phagocytosis to establish infection and cause disease. The molecular mechanisms underlying entry are still poorly understood. Here, we report that an intact sphingolipid biosynthetic pathway is essential for the uptake of by phagocytes. Disrupting sphingolipid production affects the segregation of the regulatory phosphatase CD45 from the nascent phagosome, a critical step in the progression of phagocytosis. We also show that blocking sphingolipid biosynthesis impairs activation of small GTPases and phosphoinositide turnover at the host-pathogen contact sites. Moreover, production of sphingomyelin, not glycosphingolipids, is critical for the phagocytic uptake of These data demonstrate a vital role for sphingomyelin biosynthesis in an early step of infection, defining a potential target for antimycobacterial therapeutics.