High Glucose-Induced Pyruvate Kinase M2 (PKM2) Tyrosine Phosphorylation Drives a Feedback Loop by PDGFRβ to Force mTORC1 Activation for Mesangial Cell (MC) Injury in Diabetic Nephropathy (DN)
- Diabetic Kidney Disease: Basic - I
November 03, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Diabetic Kidney Disease
- 701 Diabetic Kidney Disease: Basic
- Das, Falguni, UTHSCSA, San Antonio, Texas, United States
- Ghosh-choudhury, Nandini, UTHSCSA, San Antonio, Texas, United States
- Kasinath, Balakuntalam S., UTHSCSA, San Antonio, Texas, United States
- Ghosh-Choudhury, Goutam, South Texas VAMC, San Antonio, Texas, United States
Besides its role in the last step of glycolysis to produce pyruvate, increased expression and tyrosine phosphorylation of PKM2 regulate mitotic checkpoint in many cancers . We investigated the role of PKM2 tyrosine phosphorylation in DN.
MCs, OVE26 and db/db mice were employed.
Incubation of MCs with 25 mM glucose (HG) increased the expression of PKM2 in a sustained manner. HG induced translocation of PKM2 into the nucleus and increased its phosphorylation at tyrosine-105 residue in both cytosol and nucleus. We have recently shown a role of PDGFRβ in DN. We hypothesized that PDGFRβ may regulate PKM2. JNJ, a PDGFRβ inhibitor, abrogated HG-stimulated PKM2 expression and tyrosine phosphorylation. Interestingly, expression of kinase dead PKM2 K367M and tyrosine phosphorylation deficient PKM2 Y105F mutants inhibited HG-induced MC hypertrophy. In contrast, overexpression of wild type PKM2 induced MC hypertrophy similar to HG treatment. Mesangial matrix expansion is an aspect of DN. Both PKM2 K367KM and PKM2Y105F mutants mitigated HG-stimulated expression of fibronectin, collagen I (α2) and PAI-1 whereas, overexpression of PKM2 had the opposite effects similar to HG. Previously, we reported that Akt/mTORC1 signaling regulates MC pathologies. We found that PKM2 K367M and PKM2 Y105F mutants suppressed HG-stimulated Akt and mTORC1 while overexpression of PKM2 increased their activities. Intriguingly, Akt and mTORC1 inhibitors MK2206 and rapamycin, respectively, suppressed expression and tyrosine phosphorylation of PKM2. While addressing the in vivo relevance, we found increased PKM2 expression and tyrosine phosphorylation concomitant with fibronectin, PAI-1 and collagen I (α2) expression in the renal cortex of OVE26 and db/db mice, models of type 1 and type 2 diabetes, respectively.
Our results identify a previously unrecognized HG-stimulated novel positive feedback loop involving PDGFRβ, activated Akt/mTORC1 and tyrosine phosphorylated PKM2 to drive MC pathologies in DN.
- Veterans Affairs Support