Glycogen synthase kinase 3beta is a novel regulator of high glucose- and high insulin-induced extracellular matrix protein synthesis in renal proximal tubular epithelial cells.
High glucose (30 mM) and high insulin (1 nM), pathogenic factors of type 2 diabetes, increased mRNA expression and synthesis of lamininbeta1 and fibronectin after 24 h of incubation in kidney proximal tubular epithelial (MCT) cells. We tested the hypothesis that inactivation of glycogen synthase kinase 3beta (GSK3beta) by high glucose and high insulin induces increase in synthesis of laminin beta1 via activation of eIF2Bepsilon. Both high glucose and high insulin induced Ser-9 phosphorylation and inactivation of GSK3beta at 2 h that lasted for up to 48 h. This was associated with dephosphorylation of eIF2Bepsilon and eEF2, and increase in phosphorylation of 4E-BP1 and eIF4E. Expression of the kinase-dead mutant of GSK3beta or constitutively active kinase led to increased and diminished laminin beta1 synthesis, respectively. Incubation with selective kinase inhibitors showed that high glucose- and high insulin-induced laminin beta1 synthesis and phosphorylation of GSK3beta were dependent on PI 3-kinase, Erk, and mTOR. High glucose and high insulin augmented activation of Akt, Erk, and p70S6 kinase. Dominant negative Akt, but not dominant negative p70S6 kinase, inhibited GSK3beta phosphorylation induced by high glucose and high insulin, suggesting Akt but not p70S6 kinase was upstream of GSK3beta. Status of GSK3beta was examined in vivo in renal cortex of db/db mice with type 2 diabetes at 2 weeks and 2 months of diabetes. Diabetic mice showed increased phosphorylation of renal cortical GSK3beta and decreased phosphorylation of eIF2Bepsilon, which correlated with renal hypertrophy at 2 weeks, and increased laminin beta1 and fibronectin protein content at 2 months. GSK3beta and eIF2Bepsilon play a role in augmented protein synthesis associated with high glucose- and high insulin-stimulated hypertrophy and matrix accumulation in renal disease in type 2 diabetes.
Mariappan
Meenalakshmi M
MM
Department of Medicine, The University of Texas Health Science Center, San Antonio, Texas 78229, USA.
Shetty
Megan
M
Sataranatarajan
Kavithalakshmi
K
Choudhury
Goutam Ghosh
GG
Kasinath
Balakuntalam S
BS
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D018797:Cell Cycle Proteins; D002461:Cell Line, Transformed; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism* / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology; D020717:Eukaryotic Initiation Factor-2B / Q000235:genetics / Q000378:metabolism; D039561:Eukaryotic Initiation Factor-4E / Q000235:genetics / Q000378:metabolism; D039642:Eukaryotic Initiation Factors; D005353:Fibronectins / Q000096:biosynthesis / Q000235:genetics; D005947:Glucose / Q000378:metabolism / Q000494:pharmacology*; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D006984:Hypertrophy; D007004:Hypoglycemic Agents / Q000378:metabolism / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology*; D007674:Kidney Diseases / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology; D007797:Laminin / Q000096:biosynthesis* / Q000235:genetics; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism; D020652:Peptide Elongation Factor 2 / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects*; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000235:genetics / Q000378:metabolism; D013549:Sweetening Agents / Q000378:metabolism / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases; D013997:Time Factors
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D020717:Eukaryotic Initiation Factor-2B; D039561:Eukaryotic Initiation Factor-4E; D039642:Eukaryotic Initiation Factors; D005353:Fibronectins; D005947:Glucose; D038362:Glycogen Synthase Kinase 3; D000071679:Glycogen Synthase Kinase 3 beta; D007004:Hypoglycemic Agents; D007328:Insulin; D007797:Laminin; D019950:Mitogen-Activated Protein Kinase 1; D020652:Peptide Elongation Factor 2; D019869:Phosphatidylinositol 3-Kinases; D010750:Phosphoproteins; D017853:Phosphotransferases (Alcohol Group Acceptor); D051057:Proto-Oncogene Proteins c-akt; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D013549:Sweetening Agents; D058570:TOR Serine-Threonine Kinases; C499527:Eif4ebp1 protein, mouse; C546843:mTOR protein, mouse; C000605507:Gsk3b protein, mouse