# Membrane trafficking in innate immunity to bacterial pathogens

> **NIH NIH R01** · THOMAS JEFFERSON UNIVERSITY · 2022 · $390,000

## Abstract

SUMMARY
Anti-bacterial inflammatory responses in phagocytes are initiated by recognition of common pathogen
associated molecular patterns (PAMPs) by innate immune receptors. PAMP binding to membrane-associated
toll-like receptors (TLRs) at distinct subcellular sites triggers site-specific responses, and bacteria that
compromise phagosomal membranes additionally trigger cytoplasmic receptors, some of which assemble into
multisubunit inflammasomes that process and release IL-1 family cytokines. Membrane dynamics within host
phagocytes dramatically influence TLR and inflammasome localization and signaling, but host regulation of
such dynamics has been relatively unexplored. Our studies in a genetic disease model identified the
endosomal adaptor complex AP-3 as a central hub for intracellular trafficking pathways that regulate both TLR
and inflammasome responses to phagocytosed bacteria in dendritic cells (DCs) - immune cells that link innate
responses to adaptive immunity. However, AP-3 impacts these responses indirectly, reflecting AP-3's central
role in endolysosomal protein sorting. We hypothesize that defining direct targets of AP-3 sorting will elucidate
new membrane pathways controlling innate signaling and downstream anti-bacterial immune responses.
AP-3 sorts cargoes on endosomes into vesicles bound for lysosomes, phagosomes or related organelles. We
hypothesize that innate signaling defects in AP-3-deficient DCs reflect depletion of AP-3 cargoes from these
organelles. Preliminary data suggest that one such cargo is PI4K2α, an enzyme that generates the lipid
phosphatidylinositol-4-phosphate to recruit TLRs via their proinflammatory adaptors to membranes. Aim 1 will
test whether phagosomal PI4K2α recruits TLRs to initiate pro-inflammatory signaling and antigen presentation.
Other putative AP-3 cargoes include lysosomal transporters that function in lysosome homeostasis. We
hypothesize that depletion of such cargoes triggers a lysosome-dependent signaling cascade that promotes
inflammasome silencing by autophagy. Aim 2 will test whether and how lysosomal disruption impacts
inflammasome activity, and Aim 3 will test whether depletion of specific candidate lysosomal membrane
channels similarly silence inflammasomes and impact lysosome signaling and adaptive immune responses.
Fulfillment of the following Specific Aims will elucidate novel pathways that are potentially targeted by genetic
disease and/or by pathogen interference to compromise host immunity to bacterial pathogens.
1. To test whether TLR signaling from phagosomes and downstream responses are regulated by the
AP-3-associated PtdIns-4-kinase PI4K2α.
2. To test whether impaired lysosomal function dampens inflammasome activity through nutrient-
dependent signaling.
3. To test whether lysosomal membrane transporter expression influences inflammasome activation.

## Key facts

- **NIH application ID:** 10488183
- **Project number:** 5R01AI137173-06
- **Recipient organization:** THOMAS JEFFERSON UNIVERSITY
- **Principal Investigator:** Adriana Rita Mantegazza
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $390,000
- **Award type:** 5
- **Project period:** 2018-09-14 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10488183

## Citation

> US National Institutes of Health, RePORTER application 10488183, Membrane trafficking in innate immunity to bacterial pathogens (5R01AI137173-06). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10488183. Licensed CC0.

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