Ehrlichia activation of Wnt-PI3K-mTOR signaling inhibits autolysosome generation and autophagic destruction by the mononuclear phagocyte

Taslima T. Lina, Tian Luo, Thangam Sudha Velayutham, Seema Das, Jere W. McBridea

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

In multicellular organisms, autophagy is induced as an innate defense mechanism. Notably, the obligate intracellular bacterium Ehrlichia chaffeensis resides in early endosome-like vacuoles and circumvents lysosomal fusion through an unknown mechanism, thereby avoiding destruction in the autophagolysosome. In this report, we reveal that Wnt signaling plays a crucial role in inhibition of lysosomal fusion and autolysosomal destruction of ehrlichiae. During early infection, autophagosomes fuse with ehrlichial vacuoles to form an amphisome indicated by the presence of autophagy markers such as LC3 (microtubule-associated protein 1 light chain 3), Beclin-1, and p62. LC3 colocalized with ehrlichial morulae on days 1, 2, and 3 postinfection, and increased LC3II levels were detected during infection, reaching a maximal level on day 3. Ehrlichial vacuoles did not colocalize with the lysosomal marker LAMP2, and lysosomes were redistributed and dramatically reduced in level in the infected cells. An inhibitor specific for the Wnt receptor signaling component Dishevelled induced lysosomal fusion with ehrlichial inclusions corresponding to p62 degradation and promoted transcription factor EB (TFEB) nuclear localization. E. chaffeensis infection activated the phosphatidylinositol 3-kinase (PI3K)-Akt-mTOR (mechanistic target of rapamycin) pathway, and activation was induced by three ehrlichial tandem repeat protein (TRP) effectors, with TRP120 inducing the strongest activation. Moreover, induction of glycogen synthase kinase-3 (GSK3) performed using a Wnt inhibitor and small interfering RNA (siRNA) knockdown of critical components of PI3K-GSK3-mTOR signaling decreased ehrlichial survival. This report reveals Ehrlichia exploitation of the evolutionarily conserved Wnt pathway to inhibit autolysosome generation, thereby leading to evasion of this important innate immune defense mechanism.

Original languageEnglish (US)
Article numbere00690-17
JournalInfection and Immunity
Volume85
Issue number12
DOIs
StatePublished - Jan 1 2017

Fingerprint

Ehrlichia
Phosphatidylinositol 3-Kinase
Ehrlichia chaffeensis
Phagocytes
Vacuoles
Glycogen Synthase Kinase 3
Microtubule-Associated Proteins
Autophagy
Wnt Receptors
Infection
Light
Morula
Wnt Signaling Pathway
Tandem Repeat Sequences
Endosomes
Sirolimus
Lysosomes
Small Interfering RNA
Transcription Factors
Bacteria

Keywords

  • Autophagy
  • Ehrlichia chaffeensis
  • Lysosome
  • Wnt

ASJC Scopus subject areas

  • Parasitology
  • Microbiology
  • Immunology
  • Infectious Diseases

Cite this

Ehrlichia activation of Wnt-PI3K-mTOR signaling inhibits autolysosome generation and autophagic destruction by the mononuclear phagocyte. / Lina, Taslima T.; Luo, Tian; Velayutham, Thangam Sudha; Das, Seema; McBridea, Jere W.

In: Infection and Immunity, Vol. 85, No. 12, e00690-17, 01.01.2017.

Research output: Contribution to journalArticle

Lina, Taslima T. ; Luo, Tian ; Velayutham, Thangam Sudha ; Das, Seema ; McBridea, Jere W. / Ehrlichia activation of Wnt-PI3K-mTOR signaling inhibits autolysosome generation and autophagic destruction by the mononuclear phagocyte. In: Infection and Immunity. 2017 ; Vol. 85, No. 12.
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