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Role for the SRC family kinase Fyn in sphingolipid acquisition by chlamydiae

Jeffrey Mital1, Ted Hackstadt

  • 1Host-Parasite Interactions Section, Laboratory of Intracellular Parasites, NIAID, NIH, Rocky Mountain Laboratories, 903 South 4th Street, Hamilton, MT 59840, USA.

Infection and Immunity
|September 8, 2011
PubMed

Insights

Researchers identified host proteins affecting sphingomyelin trafficking to the Chlamydia trachomatis inclusion. The Src family tyrosine kinase Fyn is crucial for this process, impacting bacterial replication and development.

Area of Science:

  • Microbiology
  • Cell Biology
  • Infectious Diseases

Background:

  • Chlamydia trachomatis is an obligate intracellular bacterial pathogen that replicates within a host-derived vacuole called the inclusion.
  • Chlamydiae manipulate host cell functions from within the inclusion to ensure their survival and replication.
  • Sphingomyelin is a key lipid component of host cell membranes and is trafficked to the chlamydial inclusion.

Purpose of the Study:

  • To identify host proteins involved in the trafficking of sphingomyelin to the chlamydial inclusion using a small interfering RNA (siRNA) screen.
  • To investigate the role of specific identified host proteins, particularly the Src family tyrosine kinase Fyn, in sphingomyelin trafficking and chlamydial development.

Main Methods:

  • A small interfering RNA (siRNA)-based screening protocol was employed to systematically downregulate host proteins.
  • Quantitative assays were used to measure sphingomyelin trafficking to the chlamydial inclusion in infected cells.
  • The impact of Fyn silencing and Src family kinase inhibition on sphingomyelin cellular retention and incorporation into elementary bodies was assessed.

Main Results:

  • The screen identified 26 host proteins that, upon deficiency, decreased sphingomyelin trafficking to the inclusion and 16 proteins that increased it.
  • Downregulation of the Src family tyrosine kinase Fyn significantly reduced sphingomyelin trafficking to the inclusion without affecting sphingomyelin synthesis or basal trafficking.
  • Inhibition of Src family kinases led to increased cellular sphingomyelin retention and decreased incorporation into elementary bodies of C. trachomatis and Chlamydophila caviae.

Conclusions:

  • Host protein Fyn plays a critical role in directing sphingomyelin to the chlamydial inclusion, essential for pathogen survival and replication.
  • Targeting Src family kinases disrupts sphingomyelin homeostasis within the host cell, impairing chlamydial development.
  • These findings highlight host sphingomyelin trafficking pathways as potential targets for novel anti-chlamydial therapies.

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