Regulation of macrophage activity by surface receptors contained within Borrelia burgdorferi-enriched phagosomal fractions

PLoS Pathog. 2019 Nov 18;15(11):e1008163. doi: 10.1371/journal.ppat.1008163. eCollection 2019 Nov.

Abstract

Macrophages mediate the elimination of pathogens by phagocytosis resulting in the activation of specific signaling pathways that lead to the production of cytokines, chemokines and other factors. Borrelia burgdorferi, the causative agent of Lyme disease, causes a wide variety of pro-inflammatory symptoms. The proinflammatory capacity of macrophages is intimately related to the internalization of the spirochete. However, most receptors mediating this process are largely unknown. We have applied a multiomic approach, including the proteomic analysis of B. burgdorferi-containing phagosome-enriched fractions, to identify surface receptors that are involved in the phagocytic capacity of macrophages as well as their inflammatory output. Sucrose gradient protein fractions of human monocyte-derived macrophages exposed to B. burgdorferi contained the phagocytic receptor, CR3/CD14 highlighting the major role played by these proteins in spirochetal phagocytosis. Other proteins identified in these fractions include C-type lectins, scavenger receptors or Siglecs, of which some are directly involved in the interaction with the spirochete. We also identified the Fc gamma receptor pathway, including the binding receptor, CD64, as involved both in the phagocytosis of, and TNF induction in response to B. burgdorferi in the absence of antibodies. The common gamma chain, FcγR, mediates the phagocytosis of the spirochete, likely through Fc receptors and C-type lectins, in a process that involves Syk activation. Overall, these findings highlight the complex array of receptors involved in the phagocytic response of macrophages to B. burgdorferi.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Borrelia burgdorferi / immunology*
  • Cytokines / metabolism
  • Lyme Disease / immunology*
  • Lyme Disease / metabolism
  • Lyme Disease / microbiology
  • Macrophage Activation / immunology*
  • Mice
  • Mice, Inbred C57BL
  • Phagocytosis / immunology*
  • Proteomics
  • Receptors, Cell Surface / immunology
  • Receptors, Cell Surface / metabolism*
  • Signal Transduction

Substances

  • Cytokines
  • Receptors, Cell Surface

Grants and funding

Supported by grants from the Ministry of Science, Innovation and Universities (MCIU), co-financed with FEDER funds (SAF2015-65327-R and RTI2018-096494-B-100 to JA; SAF2015-73549-JIN to HR, AGL2017-86757-R to LA, SAF2016-77433-R to RPR). We thank the MCIU for the Severo Ochoa Excellence accreditation (SEV-2016-0644), the Basque Department of Industry, Tourism and Trade (Etortek and Elkartek programs), the Innovation Technology Department of the Bizkaia Province and the CIBERehd network. ACG is a recipient of a fellowship from the Basque Government. DB and MMR are recipients of MCIU FPI fellowships. APC is a fellow from the Universidad del Pais Vasco/Euskal Herriko Unibertsitatea. LA and RPR are supported by the Ramón y Cajal Program (RYC-2013-13666 to LA and RYC-2014-15655 to RPR). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.