Microfilariae of Brugia malayi Inhibit the mTOR Pathway and Induce Autophagy in Human Dendritic Cells.
Immune modulation is a hallmark of patent filarial infection, including suppression of antigen-presenting cell function and downmodulation of filarial antigen-specific T cell responses. The mammalian target of rapamycin (mTOR) signaling pathway has been implicated in immune regulation, not only by suppressing T cell responses but also by regulating autophagy (through mTOR sensing amino acid availability). Global proteomic analysis (liquid chromatography-tandem mass spectrometry) of microfilaria (mf)-exposed monocyte-derived dendritic cells (DC) indicated that multiple components of the mTOR signaling pathway, including mTOR, eIF4A, and eIF4E, are downregulated by mf, suggesting that mf target this pathway for immune modulation in DC. Utilizing Western blot analysis, we demonstrate that similar to rapamycin (a known mTOR inhibitor), mf downregulate the phosphorylation of mTOR and its regulatory proteins, p70S6K1 and 4E-BP1, a process essential for DC protein synthesis. As active mTOR signaling regulates autophagy, we examined whether mf exposure alters autophagy-associated processes. mf-induced autophagy was reflected in marked upregulation of phosphorylated Beclin 1, known to play an important role in both autophagosome formation and autolysosome fusion, in induction of LC3II, a marker of autophagosome formation, and in induced degradation of p62, a ubiquitin-binding protein that aggregates protein in autophagosomes and is degraded upon autophagy that was reduced significantly by mf exposure and by rapamycin. Together, these results suggest that Brugia malayi mf employ mechanisms of metabolic modulation in DC to influence the regulation of the host immune response by downregulating mTOR signaling, resulting in increased autophagy. Whether this is a result of the parasite-secreted rapamycin homolog is currently under study.
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Prakash Babu
PB
Narasimhan
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Sasisekhar
S
Bennuru
Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, Maryland, USA.
Zhaojing
Z
Meng
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Rachel N
RN
Cotton
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Kathleen R
KR
Elliott
Biological Imaging Section, Research Technologies Branch, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Sundar
S
Ganesan
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Renee
R
McDonald-Fleming
Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Leidos Biomedical Research, Inc., Frederick National Laboratory, Frederick, Maryland, USA.
Timothy D
TD
Veenstra
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA.
Thomas B
TB
Nutman
Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, USA rsemnani@niaid.nih.gov.
Roshanak
R
Tolouei Semnani
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D000071182:Autophagosomes / Q000378:metabolism / Q000469:parasitology; D001343:Autophagy / Q000502:physiology*; D000071186:Beclin-1 / Q000378:metabolism; D017178:Brugia malayi / Q000469:parasitology*; D018797:Cell Cycle Proteins; D003713:Dendritic Cells / Q000378:metabolism / Q000469:parasitology*; D015536:Down-Regulation / Q000502:physiology; D039601:Eukaryotic Initiation Factor-4A / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000378:metabolism / Q000469:parasitology; D008842:Microfilariae / Q000502:physiology*; D009000:Monocytes / Q000378:metabolism / Q000469:parasitology; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D040901:Proteomics / Q000379:methods; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology
D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D000071186:Beclin-1; D018797:Cell Cycle Proteins; C087000:EIF4EBP1 protein, human; D039561:Eukaryotic Initiation Factor-4E; D010750:Phosphoproteins; D025801:Ubiquitin; C546842:MTOR protein, human; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases; D039601:Eukaryotic Initiation Factor-4A