Abstract: SA-PO120
Ablation of Type 2 IP3R, a Calcium Channel Located on the Organelle Contact Site, Improves the Repairment of Cell Survival and Endoplasmic Reticulum-Mitochondria Function in Tubular Cells
Session Information
- AKI: Metabolism and Cell Death
October 26, 2024 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Acute Kidney Injury
- 103 AKI: Mechanisms
Authors
- Li, Qi, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu, Bunkyo-ku, Tokyo, Japan
- Hasegawa, Sho, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu, Bunkyo-ku, Tokyo, Japan
- Takenaka, Yuto, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu, Bunkyo-ku, Tokyo, Japan
- Nangaku, Masaomi, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu, Bunkyo-ku, Tokyo, Japan
- Inagi, Reiko, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu, Bunkyo-ku, Tokyo, Japan
Background
The renal proximal tubules (PT) are susceptible to ischemia-reperfusion injury (IRI). The Inositol trisphosphate receptors (IP3Rs) are calcium-release channels located on endoplasmic reticulum (ER). IP3Rs, composed of 3 isoforms, mediate calcium flux from the ER to the mitochondria via mitochondria-associated ER membrane (MAM) and multiple cellular functions. However, isoform-specific IP3R function in PT cells still remains unknown.
Methods
To assess the isoform-specific IP3R function in kidney tubules, the isoforms were separately knocked down in the human proximal tubular cell line, HK-2 cells. As a mimic of IRI, HK-2 cells were exposed to 24h anoxia followed by 4h reperfusion (AR) and assessed the cell fate and organelle function by corresponding assays and fluorescent probes.
Results
Among 3 isoforms, knocking down IP3R2 in HK-2 cells decreased the cell number stacked in the cell cycle G1 phase and improved the cell proliferation rate under the AR conditions. In contrast, knocking down IP3R1 or IP3R3 did not protect the cells from G1 arrest. Interestingly, IP3R2 knockdown did not alter the AR-induced calcium flux after AR, a major MAM function in ER-mitochondrial interaction. Mechanistically, IP3R2 knockdown reduced the AR-induced p27 upregulation, which promotes the CDK2 activity, leading to the cell's entry to an efficient S phase. It was consistent with that induction of senescence-associated secretory phenotype (SASP: TGF-b1 and IL-6) by AR was significantly ameliorated by IP3R2 knockdown. Importantly, the IP3R2 knockdown ameliorated organelle stress caused by AR: ER stress and mitochondrial stress (depolarization and dynamics) were ameliorated by IP3R2 knockdown, but not IP3R1 and IP3R3.
Conclusion
IP3R2 knockdown improved cell cycle status and ER-mitochondria function in PT cells with AR injury, suggesting the novel pathophysiological significance for IP3R2 on cell fate and ER-mitochondrial homeostasis under IRI by a calcium flux-independent pathway.
Funding
- Government Support – Non-U.S.