Abstract: FR-OR066
APOL1 Variants Promote T Cell Excitation by Modulating Calcium (Ca2+) Signaling Downstream of T Cell Receptors (TCRs) in Graft Rejection
Session Information
- Transplantation: Basic Science Innovations and Advances
November 07, 2025 | Location: Room 370A, Convention Center
Abstract Time: 04:50 PM - 05:00 PM
Category: Transplantation
- 2101 Transplantation: Basic
Authors
- Pell, John F., Yale University, New Haven, Connecticut, United States
- Tanvir, E M, Yale University, New Haven, Connecticut, United States
- Sun, Zeguo, Icahn School of Medicine at Mount Sinai, New York, New York, United States
- Azzi, Jamil R., Harvard Medical School, Boston, Massachusetts, United States
- Murakami, Naoka, Washington University in St Louis School of Medicine, St. Louis, Missouri, United States
- Reghuvaran, Anand, Yale University, New Haven, Connecticut, United States
- Kumar, Ashwani, Yale University, New Haven, Connecticut, United States
- Barsotti, Gabriel, Yale University, New Haven, Connecticut, United States
- Ishibe, Shuta, Yale University, New Haven, Connecticut, United States
- Heeger, Peter S., Cedars-Sinai Medical Center, Los Angeles, California, United States
- Menon, Madhav C., Yale University, New Haven, Connecticut, United States
Background
Exonic variants in Apolipoprotein-L1 (APOL1-RVs G1 and -G2) increase ESRD-risk vs. the major allele (G0). Multiple data have linked APOL1-RVs in kidney recipients with allograft rejection, but underpinning causal mechanisms are unknown.
Methods
We used BAC-transgenic mice (BAC-Tg) for G0-, G1- or G2-APOL1 expression under the human APOL1 promoter to investigate T-cell phenotype and function, and the CTOT-19 transplant cohort (n=226) to correlate in vivo findings.
Results
Adult G1-BAC-Tg-CD8+T-cells showed more surface APOL1-expression vs G0 and activation, proliferation & central memory (Tcm) expansion after ex-vivo TCR-stimulation, which were reversed with specific APOL1 inhibition (MZ-302). Analogously, APOL1-RVs in CTOT-19 with rejection had increased Tcms pre-transplant (vs G0). In MHC-mismatched cardiac transplants, G1-mice had greater CD8+T-cell infiltration and reduced survival. Bulk RNA-seq of ex-vivo stimulated naïve CD8+T-cells and scRNA-seq of graft infiltrating Tcms showed enrichment of canonical TCR pathways, particularly for Ca2+-signaling. G1-CD8+T-cells had increases in delayed Ca2+ entry with TCR stimulation (+CD3) but reduced early cytosolic Ca2+ entry vs. G0s following addition of Thapsigargin, demonstrating pre-existing ER Ca2+ leak in G1-T-cells, a driver of store-operated calcium entry (SOCE). To test IP3-Ca2+ channel-mediated ER-Ca2+ leak, we inhibited IP3-Ca2+ channels (Xestospongin), observing disproportionate inhibition of proliferation in G1-CD8+T-cells. SOCE inhibition (YM58483) or Ca2+ chelation (BAPTA) at low doses abolished increased proliferation observed in G1 mice, confirming the role of Ca2+ signaling in APOL1-mediated CD8+ T-cell activation.
Conclusion
We unravel an excitatory T-cell intrinsic mechanism for APOL1 exonic variants, causally linking them with kidney rejection.
Funding
- Other U.S. Government Support