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The CD40-autophagy pathway is needed for host protection despite IFN-Γ-dependent immunity and CD40 induces autophagy via control of P21 levels.

Abstract
Autophagy degrades pathogens in vitro. The autophagy gene Atg5 has been reported to be required for IFN-γ-dependent host protection in vivo. However, these protective effects occur independently of autophagosome formation. Thus, the in vivo role of classic autophagy in protection conferred by adaptive immunity and how adaptive immunity triggers autophagy are incompletely understood. Employing biochemical, genetic and morphological studies, we found that CD40 upregulates the autophagy molecule Beclin 1 in microglia and triggers killing of Toxoplasma gondii dependent on the autophagy machinery. Infected CD40(-/-) mice failed to upregulate Beclin 1 in microglia/macrophages in vivo. Autophagy-deficient Beclin 1(+/-) mice, mice with deficiency of the autophagy protein Atg7 targeted to microglia/macrophages as well as CD40(-/-) mice exhibited impaired killing of T. gondii and were susceptible to cerebral and ocular toxoplasmosis. Susceptibility to toxoplasmosis occurred despite upregulation of IFN-γ, TNF-α and NOS2, preservation of IFN-γ-induced microglia/macrophage anti-T. gondii activity and the generation of anti-T. gondii T cell immunity. CD40 upregulated Beclin 1 and triggered killing of T. gondii by decreasing protein levels of p21, a molecule that degrades Beclin 1. These studies identified CD40-p21-Beclin 1 as a pathway by which adaptive immunity stimulates autophagy. In addition, they support that autophagy is a mechanism through which CD40-dependent immunity mediates in vivo protection and that the CD40-autophagic machinery is needed for host resistance despite IFN-γ.
AuthorsJose-Andres C Portillo, Genevieve Okenka, Erin Reed, Angela Subauste, Jennifer Van Grol, Katrin Gentil, Masaaki Komatsu, Keiji Tanaka, Gary Landreth, Beth Levine, Carlos S Subauste
JournalPloS one (PLoS One) Vol. 5 Issue 12 Pg. e14472 ( 2010) ISSN: 1932-6203 [Electronic] United States
PMID21217818 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
Chemical References
  • Antigens, CD40
  • Apoptosis Regulatory Proteins
  • Becn1 protein, mouse
  • Tumor Necrosis Factor-alpha
  • Interferon-gamma
  • Nitric Oxide Synthase Type II
  • Nos2 protein, mouse
  • p21-Activated Kinases
Topics
  • Animals
  • Antigens, CD40 (biosynthesis, chemistry)
  • Apoptosis Regulatory Proteins (biosynthesis)
  • Autophagy
  • Gene Expression Regulation
  • Genetic Predisposition to Disease
  • Immune System
  • Interferon-gamma (metabolism)
  • Mice
  • Mice, Inbred C57BL
  • Nitric Oxide Synthase Type II (metabolism)
  • Phagosomes (metabolism)
  • Toxoplasma (genetics)
  • Toxoplasmosis (genetics, parasitology)
  • Tumor Necrosis Factor-alpha (metabolism)
  • p21-Activated Kinases (metabolism)

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