Oral Presentation CD1-MR1 2024

Two-pore channel endosomal calcium signaling enables MR1 presentation of Mycobacterium tuberculosis (#3)

Allison E Tammen 1 , Elham Karamooz 2 3 , Jessie Peterson 2 , Andrew J Olive 4 , David M Lewinsohn 1 2 3
  1. Molecular Microbiology & Immunology, Oregon Health and Science University, Portland, OREGON, United States
  2. Research and Development, VA Portland Health Care System, Portland, OR
  3. Pulmonary, Allergy, & Critical Care Medicine, Oregon Health & Science University, Portland, OR
  4. Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan

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 can present Mtb-derived riboflavin metabolites to MR1-restricted T cells (MR1Ts)1,2. Our laboratory has found that endosomal trafficking facilitates MR1 antigen presentation3,4, yet the exact mechanisms by which MR1 loading and trafficking to the cell surface occur are not known. We have found that endosomal calcium signaling mediates MR1 antigen presentation during Mtb infection5. Interference of two-pore calcium channels (TPCs) via siRNA-mediated knockdown or treatment with a selective NAADP (nicotinic acid adenine dinucleotide phosphate) antagonist reduces MR1 antigen presentation of Mtb metabolites5. Additionally, MR1 antigen presentation of Mtb metabolites was reduced when TPC1 was knocked out. NAADP acts as a second messenger for lysosomal calcium release by activating TPCs. Here, we demonstrate that siRNA-mediated knockdown of Sm-like Protein 12 (Lsm12), an NAADP binding protein, decreases MR1 antigen presentation of the Mtb-infected cell. These data indicate NAADP facilitates MR1 antigen presentation of Mycobacterial metabolites via the TPC. NAADP is synthesized from NADP, and this reaction requires catalysis by ADP-ribosyl cyclase. We found that interference of ADP-ribosyl cyclase activity via treatment with a quinolone carboxamide inhibitor that targets the ADP-ribosyl cyclase domain6 reduces MR1 antigen presentation of Mtb metabolites. These data suggest this enzymatic activity is important. We are investigating proteins that possess this enzymatic activity, such as our leading candidate Cluster of Differentiation 38 (CD38), via siRNA-mediated knockdowns to further elucidate requirements for MR1 antigen presentation of Mtb metabolites. Together, these findings suggest a unique role for endosomal calcium sensing in the recognition of the Mtb-infected cell.

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