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ARS Home » Northeast Area » Boston, Massachusetts » Jean Mayer Human Nutrition Research Center On Aging » Research » Publications at this Location » Publication #307550
Title: Newborn mouse lens proteome and its alteration by lysine 6 mutant ubiquitin

Author
item SHANG, FU - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item WILMARTH, PHILLIP - Oregon Health & Science University
item CHANG, MIN LEE - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item LIU, KE - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item DAVID, LARRY - Oregon Health & Science University
item CACERES, MARIA ANDREA - Jean Mayer Human Nutrition Research Center On Aging At Tufts University
item WAWROUSEK, ERIC - National Institutes Of Health (NIH)
item TAYLOR, ALLEN - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Journal of Proteome Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2013
Publication Date: 1/22/2014
Citation: Shang, F., Wilmarth, P.A., Chang, M., Liu, K., David, L., Caceres, M., Wawrousek, E., Taylor, A. 2014. Newborn mouse lens proteome and its alteration by lysine 6 mutant ubiquitin. Journal of Proteome Research. 13(3):1177-1789.

Interpretive Summary: The eye lens is a transparent organ that collects and focuses light onto the retina for clear vision. The lens contains highest levels of proteins in the body. The total protein amount and relative levels of each individual component determine the structure and function of the lens. The compositions of lens proteins are maintained by the balance between protein synthesis and protein degradation. Ubiquitin is a small protein that targets other proteins for degradation. We found that production of mutant ubiquitin (K6W-ubiquitin) in the lens results in defects in lens development and lens transparency. To investigate how mutant ubiquitin affects lens development and lens transparency, we determined the effects of mutant ubiquitin on lens protein composition of newborn mice. We identified a total of 2052 proteins in the lens and quantitatively compared the levels of 996 between normal lens and lenses that produce K6W-ubiquitin. We found that the levels of many proteins that were only produced in the lens were dramatically altered by K6W-ubiquitin. These include a major class of proteins called gamma-crystallins and proteins that are involved in energy metabolism, signal transduction and protein degradation. Together, these data suggest that the alteration of lens protein composition is a direct cause of lens structural abnormality.

Technical Abstract: Ubiquitin is a tag that often initiates degradation of proteins by the proteasome in the ubiquitin proteasome system. Targeted expression of K6W mutant ubiquitin (K6W-Ub) in the lens results in defects in lens development and cataract formation, suggesting critical functions for ubiquitin in lens. To study the developmental processes that require intact ubiquitin, we executed the most extensive characterization of the lens proteome to date. We quantified lens protein expression changes in multiple replicate pools of P1 wild-type and K6W-Ub-expressing mouse lenses. Lens proteins were digested with trypsin, peptides were separated using strong cation exchange and reversed-phase liquid chromatography, and tandem mass (MS/MS) spectra were collected with a linear ion trap. Transgenic mice that expressed low levels of K6W-Ub (low expressers) had normal, clear lenses at birth, whereas the lenses that expressed high levels of K6W-Ub (higher expressers) had abnormal lenses and cataracts at birth. A total of 2052 proteins were identified, of which 996 were reliably quantified and compared between wild-type and K6W-Ub transgenic mice. Consistent with a delayed developmental program, fiber-cell-specific proteins, such as gamma-crystallins (gamma-A, gamma-B, gamma-C, and gamma-E), were down-regulated in K6W-Ub higher expressers. Up-regulated proteins were involved in energy metabolism, signal transduction, and proteolysis. The K6W-Ub low expressers exhibited delayed onset and milder cataract consistent with smaller changes in protein expression. Because lens protein expression changes occurred prior to lens morphological abnormalities and cataract formation in K6W-Ub low expressers, it appears that expression of K6W-Ub sets in motion a process of altered protein expression that results in developmental defects and cataract.