Following ischemic injury, surviving kidney proximal tubule cells dedifferentiate and proliferate to regenerate the tubules. After reaching critical cell densities, growth arrest and differentiation follow. The signaling mechanisms that govern this process are important and critically determine structural and functional recovery from ischemic injury. Our research suggests that the phosphatidylinositol 3-kinase (PI3K) signaling pathway may play an important role in proximal tubule cell proliferation and regeneration. We observed that the suppression of PI3K signaling associated with growth arrest of cultured proximal tubule cells is accompanied by an increase in the cellular content of the tumor suppressor protein PTEN. This suggests that PTEN might regulate proximal tubule proliferation through the lipid phosphatase actions of PTEN that would decrease the levels of D-3 phosphorylated inositol phospholipids made by PI3K. Our preliminary studies suggest that the increase of PTEN associated with growth inhibition is caused by at least two feedback mechanisms of autoregulatory signaling: one is driven by Akt, a downstream member of the PI3K pathway and the other by intercellular contact as cell numbers increase. We plan to use cell culture and in vivo models to unravel molecular mechanisms of proximal tubule cell growth regulation. Our research will use 5 approaches to study how PTEN regulates growth, and how PTEN is regulated. (1) We will employ PTEN vectors and siRNA methods to increase or decrease PTEN protein and activity. (2) We will use a constitutively expressed Akt construct that permits rapid and selective induction of Akt kinase activity to study how Akt activation leads to PTEN upregulation. (3) We will disrupt and restore cell junctions in cultured proximal tubule cells to study how cell contact leads to regulation of PTEN. Regulation of PTEN will be studied at the levels of transcription, mRNA stability and protein turnover. (4) We will use genomics and proteomics approaches to identify novel proteins involved in PTEN regulation. (5) We will study regulation of PI3K signaling by PTEN in vivo in rats and mice with ischemic acute renal failure using biochemical methods, immuno histochemistry and in situ hybridization. We will employ PTEN antisense oligonucleotides to suppress kidney PTEN in vivo to study how this intervention affects the course of proximal tubule regeneration and recovery.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK037139-22
Application #
7456447
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Hoshizaki, Deborah K
Project Start
1987-07-01
Project End
2010-06-30
Budget Start
2008-07-01
Budget End
2010-06-30
Support Year
22
Fiscal Year
2008
Total Cost
$463,784
Indirect Cost
Name
University of Texas Health Science Center San Antonio
Department
Pathology
Type
Schools of Medicine
DUNS #
800772162
City
San Antonio
State
TX
Country
United States
Zip Code
78229
Venkatachalam, Manjeri A; Weinberg, Joel M (2017) Pericytes Preserve Capillary Integrity to Prevent Kidney Hypoxia. J Am Soc Nephrol 28:717-719
Lan, Rongpei; Geng, Hui; Singha, Prajjal K et al. (2016) Mitochondrial Pathology and Glycolytic Shift during Proximal Tubule Atrophy after Ischemic AKI. J Am Soc Nephrol 27:3356-3367
Kallingal, George J S; Weinberg, Joel M; Reis, Isildinha M et al. (2016) Long-term response to renal ischaemia in the human kidney after partial nephrectomy: results from a prospective clinical trial. BJU Int 117:766-74
Weinberg, Joel M; Bienholz, Anja; Venkatachalam, M A (2016) The role of glycine in regulated cell death. Cell Mol Life Sci 73:2285-308
Venkatachalam, Manjeri A; Weinberg, Joel M (2015) Fibrosis without fibroblast TGF-? receptors? Kidney Int 88:434-7
Singha, P K; Pandeswara, S; Venkatachalam, M A et al. (2013) Manumycin A inhibits triple-negative breast cancer growth through LC3-mediated cytoplasmic vacuolation death. Cell Death Dis 4:e457
Lan, Rongpei; Geng, Hui; Polichnowski, Aaron J et al. (2012) PTEN loss defines a TGF-?-induced tubule phenotype of failed differentiation and JNK signaling during renal fibrosis. Am J Physiol Renal Physiol 302:F1210-23
Geng, Hui; Lan, Rongpei; Singha, Prajjal K et al. (2012) Lysophosphatidic acid increases proximal tubule cell secretion of profibrotic cytokines PDGF-B and CTGF through LPA2- and G?q-mediated Rho and ?v?6 integrin-dependent activation of TGF-?. Am J Pathol 181:1236-49
Lan, Rongpei; Geng, Hui; Hwang, Yoon et al. (2010) A novel wounding device suitable for quantitative biochemical analysis of wound healing and regeneration of cultured epithelium. Wound Repair Regen 18:159-67
Venkatachalam, Manjeri A; Griffin, Karen A; Lan, Rongpei et al. (2010) Acute kidney injury: a springboard for progression in chronic kidney disease. Am J Physiol Renal Physiol 298:F1078-94

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