Over-expression of insulin-response element binding protein-1 (IRE-BP1) in mouse pancreatic islets increases expression of RACK1 and TCTP: Beta cell markers of high glucose sensitivity.
A targeted analysis of the 50kDa C-terminal fragment of insulin-response element binding protein-1 (IRE-BP1) activation of target genes through the insulin receptor substrate receptor/PI-3 kinase/Akt pathway has been demonstrated for the insulin growth factor-1 receptor. The broader effects of 50kDa C-terminal IRE-BP1 fragment over-expression on protein abundance in pancreatic islet beta cells have not been determined.



Liquid-chromatography coupled to tandem mass spectrometry (LC-MS/MS) analyses of replicate lysates of pancreatic islets isolated from background strain animals and transgenic animals, overexpressing IRE-BP1 in pancreatic islet beta cells, demonstrated statistically significant increases in the expression of proteins involved in protein synthesis, endoplasmic reticulum (ER) stress and scaffolding proteins important for protein kinase C signaling; some of which were confirmed by immunoblot analyses. Bioinformatic analysis of protein expression network patterns suggested IRE-BP1 over-expression leads to protein expression patterns indicative of activation of functional protein networks utilized for protein post-translational modification, protein folding, and protein synthesis. Co-immunoprecipitation experiments demonstrate a novel interaction between two differentially regulated proteins receptor for activated protein kinase C (RACK1) and translationally controlled tumor protein (TCTP).



Proteomic analysis of IRE-BP1 over-expression in pancreatic islet beta cells suggest IRE-BP1 (a) directly or indirectly through establishing hyperglycemia results in increased expression of ribosomal proteins and markers of ER stress and (b) leads to the enhanced and previously un-described interaction of RACK1 and TCTP.



This study identified C-terminal 50kDa domain of IRE-BP1 over-expression results in increased markers of ER-stress and a novel interaction between the scaffolding proteins RACK1 and TCTP.
Department of Medicine, University of Louisville, Louisville, KY, United States.
Betty C
BC
Villafuerte
Department of Medicine, University of Louisville, Louisville, KY, United States.
Michelle T
MT
Barati
Department of Medicine, University of Louisville, Louisville, KY, United States.
Madhavi J
MJ
Rane
Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States.
Susan
S
Isaacs
Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States.
Ming
M
Li
Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States.
Daniel W
DW
Wilkey
Department of Medicine, University of Louisville, Louisville, KY, United States; Core Proteomics Laboratory, University of Louisville, Louisville, KY, United States. Electronic address: mlmerc02@louisville.edu.
Michael L
ML
Merchant
D000818:Animals; D015415:Biomarkers / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D059865:Endoplasmic Reticulum Stress / Q000502:physiology; D005947:Glucose / Q000378:metabolism*; D006943:Hyperglycemia; D007328:Insulin / Q000378:metabolism; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D035941:Iron Regulatory Protein 1 / Q000378:metabolism*; D007515:Islets of Langerhans / Q000378:metabolism*; D051379:Mice; D009479:Neuropeptides / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000502:physiology; D040901:Proteomics / Q000379:methods; D000075370:Receptors for Activated C Kinase; D020218:Response Elements / Q000502:physiology; D000090324:Tumor Protein, Translationally-Controlled 1
D015415:Biomarkers; D014408:Biomarkers, Tumor; D007328:Insulin; D009479:Neuropeptides; C090294:RACK1 protein, mouse; D000075370:Receptors for Activated C Kinase; C000715648:Tpt1 protein, mouse; D000090324:Tumor Protein, Translationally-Controlled 1; D011493:Protein Kinase C; D035941:Iron Regulatory Protein 1; D005947:Glucose
Label-free quantification; Mass spectrometry; Proteomics; Spectral counting