Abstract: FR-PO0761
Endoplasmic Reticulum Integrity and Organelle Interactions in Living Cells Expressing INF2 Variants
Session Information
- Glomerular Diseases: Cell Homeostasis and Novel Injury Mechanisms
November 07, 2025 | Location: Exhibit Hall, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Glomerular Diseases
- 1401 Glomerular Diseases: Mechanisms, including Podocyte Biology
Authors
- Tran Thuy, Huong Quynh, Kansai Medical University, Second Department of Internal Medicine, Renal Division, Hirakata, Osaka, Japan
- Kondo, Naoyuki, Kansai Medical University, Institute of Biochemical Science, Department of Molecular Genetics, Hirakata, Osaka, Japan
- Ueda, Hiroko, Kansai Medical University, Second Department of Internal Medicine, Renal Division, Hirakata, Osaka, Japan
- Matsuo, Yoshiyuki, Kansai Medical University, Institute of Biomedical Science, Central Research Center, Hirakata, Osaka, Japan
- Tsukaguchi, Hiroyasu, Kansai Medical University, Second Department of Internal Medicine, Renal Division, Hirakata, Osaka, Japan
Background
Pathogenic variants of inverted formin 2 (INF2) CAAX isoform, which is predominantly expressed in the endoplasmic reticulum (ER), cause two disorders, focal segmental glomerulosclerosis (FSGS) and Charcot-Marie-Tooth (CMT) neuropathy. The ER is an dynamic interconnected network that extends throughout the cytoplasm and forms abundant contacts with other organelles. However, how INF2 variants affect the ER integrity remains elusive.
Methods
We studied dynamic changes in ER morphology and inter-organelle interaction by using a high-resolution live imaging of HeLa cells expressing the pathogenic INF2 variants.
Results
Cells expressing wild-type (WT) INF2 showed a predominant tubular ER with perinuclear clustering. Cells expressing INF2 FSGS variants that cause mild and intermediate disease induced more sheet-like ER, a pattern similar to observed in cells expressing WT-INF2 that were treated with actin and microtubule (MT) inhibitors. Dual CMT-FSGS INF2 variants led to more severe ER dysmorphism, with diffuse, fragmented ER and coarse INF2 aggregates. Both F-actin and MT contributed to the proper ER organization by modulating the tubule vs.sheet conformation balance, while MT arrays regulated spatial expansion of the tubular ER in the cell periphery. Pathogenic INF2 variants also induced mitochondria fragmentation and dysregulated mitochondria distribution. These mitochondrial abnormalities were more prominent in cells expressing CMT-FSGS than in those with FSGS variants, indicating that the severity of the dysfunction is linked to the degree of cytoskeletal disorganization.
Conclusion
Pathogenic INF2 variants disrupt ER continuity by altering interactions between the ER and the cytoskeleton that in turn impairs inter-organelle communication, especially at ER-mitochondria contact sites. ER continuity defects may be a common disease mechanism involved in both peripheral neuropathy and glomerulopathy.