Role for the Src Family Kinase Fyn in Sphingolipid Acquisition by Chlamydiae

Host-Parasite Interactions Section, Laboratory of Intracellular Parasites, NIAID, NIH, Rocky Mountain Laboratories, 903 South 4th Street, Hamilton, MT 59840, USA.
Infection and immunity (Impact Factor: 3.73). 09/2011; 79(11):4559-68. DOI: 10.1128/IAI.05692-11
Source: PubMed


The bacterial obligate intracellular pathogen Chlamydia trachomatis replicates within a membrane-bound vacuole termed the inclusion. From within this protective environment, chlamydiae usurp
numerous functions of the host cell to promote chlamydial survival and replication. Here we utilized a small interfering RNA
(siRNA)-based screening protocol designed to identify host proteins involved in the trafficking of sphingomyelin to the chlamydial
inclusion. Twenty-six host proteins whose deficiency significantly decreased sphingomyelin trafficking to the inclusion and
16 proteins whose deficiency significantly increased sphingomyelin trafficking to the inclusion were identified. The reduced
sphingomyelin trafficking caused by downregulation of the Src family tyrosine kinase Fyn was confirmed in more-detailed analyses.
Fyn silencing did not alter sphingomyelin synthesis or trafficking in the absence of chlamydial infection but reduced the
amount of sphingomyelin trafficked to the inclusion in infected cells, as determined by two independent quantitative assays.
Additionally, inhibition of Src family kinases resulted in increased cellular retention of sphingomyelin and significantly
decreased incorporation into elementary bodies of both C. trachomatis and Chlamydophila caviae.

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Available from: Jeffrey Mital
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    • "Activated Fyn and Src kinases localize in discrete microdomains at the inclusion that are enriched in cholesterol and overlap with a subset of Incs, including IncB, Inc101, Inc222 and Inc850 (Mital et al., 2010). Depletion of Fyn decreases C6-NBD- sphingolipid retention by both the inclusion and EBs; however, depletion of Fyn alone does not impair production of infectious progeny, indicating that SM trafficking mediated by Fyn signalling functions redundantly with other lipid trafficking pathways (Mital and Hackstadt, 2011a). SFK regulate microtubule-and dynein-dependent trafficking of the inclusion to the microtubule organizing centre (MTOC) (Mital and Hackstadt, 2011b), therefore, it is speculated that Fyn may mediate linkage of the inclusion to the microtubule network and thereby intersect SM containing vesicles trafficking along microtubules. "
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