Alpha-crystallin and heat shock protein-27 (Hsp27), the two small heat shock proteins (Hsps) found in the lens are thought to protect lens proteins from the stress, such as, oxidation and ultra violet light. In addition to functioning as chaperone proteins, they are versatile anti-apoptotic proteins. In the lens methylglyoxal (MGO) is produced as a metabolic by-product during glycolysis and its concentration is at least 20 times higher than in plasma. Lenses from diabetics have far greater MGO concentrations than lenses from nondiabetic individuals. MGO readily reacts with lysine, arginine and cysteine residues in proteins to form stable adducts, several of which have been identified in the human lens. Our recent studies on MGO modifications provided the surprising results that MGO-modification enhances the chaperone function of sHsps. Our most recent studies demonstrate that cataractous lenses contain high levels of phosphorylated Hsp27 (pHsp27) and pHsp27 is highly susceptible for modification by MGO. We also found MGO-modified alpha-crystallin is a better anti-apoptotic protein than the native unmodified protein. These intriguing observations prompted us to examine further on the MGO-induced structural alterations in sHsps, and to determine how such alterations change their functions. We have four aims.
In aim 1, we will examine in detail the structural changes resulting from exposure of sHsps to MGO. We will focus on arginine residues, because these are the most vulnerable to modification by MGO.
In aim 2, we will determine how MGO-induced modifications alter the anti-apoptotic functions of sHsps.
In aim 3, we will study the impact of MGO-induced modifications on the interaction of sHsps with other lens proteins. Finally, in aim 4, we will determine whether MGO-modification of sHsps influence their transportation into the nucleus during increased cellular stress. These studies will improve our understanding of the interplay between sHsps and metabolic pathways, and they will help us to define the role of sHsps in apoptosis of lens epithelial cells and the implications for cataract formation.

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Research Project (R01)
Project #
5R01EY016219-05
Application #
7668530
Study Section
Special Emphasis Panel (ZRG1-AED (01))
Program Officer
Araj, Houmam H
Project Start
2005-09-09
Project End
2011-08-31
Budget Start
2009-09-01
Budget End
2011-08-31
Support Year
5
Fiscal Year
2009
Total Cost
$375,061
Indirect Cost
Name
Case Western Reserve University
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
077758407
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Nahomi, Rooban B; Oya-Ito, Tomoko; Nagaraj, Ram H (2013) The combined effect of acetylation and glycation on the chaperone and anti-apoptotic functions of human ?-crystallin. Biochim Biophys Acta 1832:195-203
Nagaraj, Ram H; Nahomi, Rooban B; Shanthakumar, Shilpa et al. (2012) Acetylation of ?A-crystallin in the human lens: effects on structure and chaperone function. Biochim Biophys Acta 1822:120-9
Nagaraj, Ram H; Panda, Alok Kumar; Shanthakumar, Shilpa et al. (2012) Hydroimidazolone modification of the conserved Arg12 in small heat shock proteins: studies on the structure and chaperone function using mutant mimics. PLoS One 7:e30257
Linetsky, Mikhail; Kaid Johar, S R; Meltretter, Jasmin et al. (2011) Determination of dideoxyosone precursors of AGEs in human lens proteins. Arch Biochem Biophys 514:16-26
Miller, Antonia G; Tan, Genevieve; Binger, Katrina J et al. (2010) Candesartan attenuates diabetic retinal vascular pathology by restoring glyoxalase-I function. Diabetes 59:3208-15
Mailankot, Maneesh; Nagaraj, Ram H (2010) Induction of indoleamine 2,3-dioxygenase by interferon-gamma in human lens epithelial cells: apoptosis through the formation of 3-hydroxykynurenine. Int J Biochem Cell Biol 42:1446-54
Mailankot, Maneesh; Howell, Scott; Nagaraj, Ram H (2010) Kynurenine inhibits fibroblast growth factor 2-mediated expression of crystallins and MIP26 in lens epithelial cells. Biochim Biophys Acta 1802:609-20
Pasupuleti, N; Matsuyama, S; Voss, O et al. (2010) The anti-apoptotic function of human ?A-crystallin is directly related to its chaperone activity. Cell Death Dis 1:e31
Gangadhariah, Mahesha H; Wang, Benlian; Linetsky, Mikhail et al. (2010) Hydroimidazolone modification of human alphaA-crystallin: Effect on the chaperone function and protein refolding ability. Biochim Biophys Acta 1802:432-41
Pasupuleti, Nagarekha; Gangadhariah, Mahesha; Padmanabha, Smitha et al. (2010) The role of the cysteine residue in the chaperone and anti-apoptotic functions of human Hsp27. J Cell Biochem 110:408-19

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