Figure 5.

Mitochondrial Protein Abundance in Retinas from Young and Old DBA/2J Mice

(A) Western blots were performed with protein extracts from mice aged 2 months (the young group, Y) or 12 months (the old group, O), using various antibodies against mitochondrial proteins. A total of 17 individual retinas were evaluated for each group. The signals obtained with the antibody against β-actin (the loading control) and with two other antibodies against mitochondrial proteins are shown for five independent membranes. With the antibody against NGB, the strongest signal was detected at 17 kDa, and additional faint signals were often detected at approximately 19, 21, 25, and 34 kDa. We had previously observed the 19-kDa and 21-kDa proteins in rodent retinas.18, 20 The other signals corresponding to higher apparent molecular masses may indicate post-translational modifications such as phosphorylation⁷⁰ or dimerization of the protein.⁷¹ The bottom row shows a membrane that was incubated with antibodies against two proteins simultaneously (1 and 2). (B) Bar charts showing the means ± SEMs calculated from separate immunoblots after they were scanned and their signals quantified with the Quantity One software. The relative levels of mitochondrial proteins were normalized against β-actin signals. For each protein, p values were calculated as the difference between the signals obtained in young and old DBA/2J mice. The number of individual signals for independent retinas used for the calculations is shown for each protein below the corresponding bars.