Effect of methylglyoxal modification on stress-induced aggregation of client proteins and their chaperoning by human alphaA-crystallin.
alpha-Crystallin prevents protein aggregation under various stress conditions through its chaperone-like properties. Previously, we demonstrated that MGO (methylglyoxal) modification of alphaA-crystallin enhances its chaperone function and thus may affect transparency of the lens. During aging of the lens, not only alphaA-crystallin, but its client proteins are also likely to be modified by MGO. We have investigated the role of MGO modification of four model client proteins (insulin, alpha-lactalbumin, alcohol dehydrogenase and gamma-crystallin) in their aggregation and structure and the ability of human alphaA-crystallin to chaperone them. We found that MGO modification (10-1000 microM) decreased the chemical aggregation of insulin and alpha-lactalbumin and thermal aggregation of alcohol dehydrogenase and gamma-crystallin. Surface hydrophobicity in MGO-modified proteins decreased slightly relative to unmodified proteins. HPLC and MS analyses revealed argpyrimidine and hydroimidazolone in MGO-modified client proteins. The degree of chaperoning by alphaA-crystallin towards MGO-modified and unmodified client proteins was similar. Co-modification of client proteins and alphaA-crystallin by MGO completely inhibited stress-induced aggregation of client proteins. Our results indicate that minor modifications of client proteins and alphaA-crystallin by MGO might prevent protein aggregation and thus help maintain transparency of the aging lens.
Biswas
Ashis
A
Department of Ophthalmology and Visual Sciences, Case Western Reserve University, Cleveland, OH 44106, USA.
Wang
Benlian
B
Miyagi
Masaru
M
Nagaraj
Ram H
RH
D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D006801:Humans; D007328:Insulin / Q000737:chemistry / Q000378:metabolism; D008969:Molecular Sequence Data; D011489:Protein Denaturation / Q000187:drug effects; D011765:Pyruvaldehyde / Q000494:pharmacology*; D013696:Temperature; D038202:alpha-Crystallin A Chain / Q000235:genetics / Q000378:metabolism*
D007328:Insulin; D038202:alpha-Crystallin A Chain; D011765:Pyruvaldehyde