Abstract: FR-PO586

Activation of PI 3 Kinase (PI 3 K) by PDGF Receptor-Beta (PDGFRb) Regulates Akt-Dependent Hif1a to Express Glut1 for Mesangial Cell (MC) Hypertrophy in Response to High Glucose (HG)

Session Information

Category: Diabetes

  • 501 Diabetes Mellitus and Obesity: Basic - Experimental

Authors

  • Das, Falguni, UTHSCSA, SAN ANTONIO, Texas, United States
  • Ghosh-choudhury, Nandini, UTHSCSA, SAN ANTONIO, Texas, United States
  • Kasinath, Balakuntalam S., University of Texas Health Science Center, San Antonio, Texas, United States
  • Ghosh-Choudhury, Goutam, University of Texas Health Science Center, San Antonio, Texas, United States
Background

Hyperglycemia increases PI 3 K/Akt to induce glomerular MC hypertrophy in diabetic nephropathy (DN). In DN, increased glomerular expression of PDGFRb is reported. As a mechanism of PI 3 K/Akt activation in DN, we hypothesized involvement of this receptor tyrosine kinase.

Methods

Human MCs, siRNA transfection, immunoblotting, protein synthesis and hypertrophy assays and rat model of streptozotocin-induced DN were used.

Results

HG significantly increased tyrosine phosphorylation-dependent activation of PI 3 K in MC, concomitant with increased tyrosine phosphorylation of PDGFRb at the catalytic loop and the PI 3 K binding sites. A specific PDGFRb inhibitor, JNJ-10198409 (JNJ), blocked these phosphorylations, which resulted in inhibition of association of PI 3 K with the PDGFRb. Similarly, siRNAs against PDGFRb and the PDGFRb mutant deficient in PI 3 K binding (PDGFRbM) inhibited HG-induced phosphorylation of PI 3 K and hence Akt. PI 3 K/Akt regulates Glut1 expression via Hif1alpha (Hif1a) transcription factor. siRNAs against Glut1 significantly inhibited HG-induced protein synthesis and hypertrophy of MCs. JNJ, siPDGFRb and PDGFRbM markedly suppressed the expression of Hif1a and Glut1 in response to HG. Interestingly, siRNAs against Hif1a inhibited HG-mediated protein synthesis and hypertrophy of MCs. Furthermore, JNJ, siPDGFRb and PDGFRbM inhibited MC hypertrophy induced by HG. This inhibition was reversed by the expression of constitutively active Akt kinase or Hif1a. Moreover, expression of Glut1 prevented the inhibition of hypertrophy induced by siPDGFRb or PDGFRbM. Finally, we observed increased phosphorylation of PDGFRb and PI 3 K in the glomerular fraction of STZ-induced diabetic rat. This increased phosphorylation was associated with Hif1a and Glut1 expression in the diabetic glomeruli.

Conclusion

Together our results provide the first evidence for a role of PDGFRb-mediated PI 3 K/Akt activation to control Hif1a/Glut1 axis in HG-induced MC hypertrophy.

Funding

  • NIDDK Support