Poster Presentation CD1-MR1 Workshop 2025

NAADP-mediated endosomal calcium signaling enables MR1 presentation of Mycobacterium tuberculosis (#118)

Allison Tammen 1 , Elham Karamooz 2 3 , Jessie Peterson 2 , Corinna Kulicke 3 , David Lewinsohn 1 2 3
  1. Molecular Microbiology & Immunology, Oregon Health and Science University, Portland, OR
  2. Research and Development, VA Portland Health Care System, Portland, OR
  3. Pulmonary, Allergy, & Critical Care Medicine, Oregon Health & Science University, Portland, OR

The immune system has developed specialized mechanisms to recognize intracellular pathogens such as Mycobacterium tuberculosis (Mtb). Major Histocompatibility Complex, Class I-Related molecule (MR1) is a conserved nonclassical antigen presenting molecule that presents ligands derived from Mtb riboflavin synthesis to MR1-restricted T cells (MR1Ts)1,2. While endosomal trafficking facilitates MR1 antigen presentation3,4, the exact mechanisms by which MR1 loading of Mtb-derived ligands occurs are not known. We found that endosomal calcium signaling mediates MR1 antigen presentation during Mtb infection5. Nicotinic acid adenine dinucleotide phosphate (NAADP) acts as a second messenger for lysosomal calcium release by activating two-pore calcium channels (TPCs). Interference with TPCs via siRNA-mediated knockdown or treatment with a selective NAADP antagonist reduces MR1 antigen presentation of Mtb-derived ligands5. NAADP synthesis is catalyzed by NAD glycohydrolases or dual NADPH oxidases. Inhibition of NAD glycohydrolase activity with a quinolone carboxamide inhibitor6 reduces MR1 antigen presentation of Mtb-derived ligands. These data suggest this enzymatic activity is important. We are investigating candidate proteins that possess this enzymatic activity to further elucidate requirements for MR1 antigen presentation of Mtb-derived ligands. Together, these findings suggest a unique role for endosomal calcium sensing in the recognition of the Mtb-infected cell.

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