Kidney Week

Abstract: SA-PO101

PDZD8, a Tethering Protein of Endoplasmic Reticulum (ER)-Lysosome Interaction, Alters Tubular Inflammation in Mice with Cisplatin-Induced AKI

Session Information

• AKI: Inflammation and Cell Cycle
  October 26, 2024 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 103 AKI: Mechanisms

Authors

• Takenaka, Yuto, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu Seirigaku, Bunkyo-ku, Tokyo, Japan

Yuto Takenaka, MD

• Hasegawa, Sho, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu Seirigaku, Bunkyo-ku, Tokyo, Japan

Sho Hasegawa, MD, PhD

• Hong, Yu Ah, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu Seirigaku, Bunkyo-ku, Tokyo, Japan

Yu Ah Hong, MD, PhD

• Li, Qi, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu Seirigaku, Bunkyo-ku, Tokyo, Japan

Qi Li, MD

• Maekawa, Hiroshi, Northwestern University Feinberg School of Medicine, Chicago, Illinois, United States

Hiroshi Maekawa, MD, PhD

• Nangaku, Masaomi, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu Seirigaku, Bunkyo-ku, Tokyo, Japan

Masaomi Nangaku, MD, PhD

• Inagi, Reiko, Tokyo Daigaku Daigakuin Igakukei Kenkyuka Igakubu Seirigaku, Bunkyo-ku, Tokyo, Japan

Reiko Inagi, PhD

Background

The pathophysiological importance of organelle crosstalk in maintaining cellular homeostasis is a prominent trend. PDZD8, a tethering protein located on the ER lumen, facilitates interactions with other organelles and promotes homeostasis at organelle contact sites. We thus aim to elucidate the role of organelle crosstalk, specifically through PDZD8, in the context of AKI.

Methods

In vivo studies: 8-10 week-old male PDZD8 knockout (KO) and wild-type (WT) mice were administered 20mg/kg cisplatin and euthanized 48 hr later. Kidney injury was assessed by BUN, Cre, PAS, IHC for inflammatory molecules and RT-PCR. In vitro studies: human proximal tubular cell line (HK-2) was treated with 20mM cisplatin and assessed changes in organelle homeostasis and their effect on inflammatory response (TLR9-NFkB axis) using mass spectrometry-based immuno-precipitation proteomics and immunofluorescence microscopy for organelle function.

Results

PDZD8 KO mice improved cisplatin-induced kidney injury compared to WT mice, as indicated by lower BUN and Cre levels and less severe tubular damage. This was accompanied by a diminished activation of the NFkB inflammatory pathway and decreased NFkB-downstream inflammatory gene expression (IL6, CXCL10). In vitro studies revealed that cisplatin-induced inflammation was also reduced in PDZD8-knockdown (KD) HK-2 cells, while cisplatin damage, estimated by mitochondrial DNA leakage, was identical between WT and KD cells. Interestingly, such PDZD8-mediated tubular inflammatory signal was closely correlated with the TLR9 activation level: 1) cisplatin-exposed HK-2 cells induced the intracellular translocation of TLR9 (to the lysosome), which activates NFkB inflammatory signaling, 2) PDZD8-KD significantly impaired the TLR9 translocation/activation, leading to the reduction of NFkB-mediated tubular inflammation. Further, PDZD8-KD significantly affected the lysosomal functions, characterized by insufficient lysosomal pH, which hindered TLR9 activation. These findings suggested the critical role of PDZD8-TLR9-NFkB axis as a novel pathway for regulating tubular inflammation.

Conclusion

Tubular PDZD8 regulates TLR9-NFkB inflammatory pathway through its regulation of lysosomal function via ER-lysosome interaction.