Global Analyses of Age-Related Expression Profiles of Mouse Liver Proteins and Database Construction

Abstract

Toward making an integrated understanding of age-related homeostasis, we carried out global analyses of age-related expression profiles of mouse liver proteins. Liver protein samples prepared from nuclear, cytoplasm and mitochondria fractions of mice (C57BL/6xSJL, male) at 1,3, 6, 12, 18, 21, and 24 months of age (n=10-20/age point) were subjected to quantitative analyses by 2DE (pH range 4-11) and MALDI-TOF/MS. For nuclear protein fraction, approximately 8000 protein spots separated on 2DE were analyzed by MALDI-TOF/MS for, and 4547 protein spots were identified by MASCOT protein identifier program with reasonable scores. After removing duplicated spots, 3113 protein spots were found unique, composed of 2534 single protein spots and 579 mixture protein spots. Single protein spots were subjected to quantitative analyses with a PDQuest program, generating agerelated expression profiles. GeneSpring software was then used for clustering and filtering analyses of the profiles. In addition to many complex age-related expression profiles, about a dozen unique and fundamental age-related profiles were identified. Many isomers, likely generated mostly by posttranslational modifications and/or by alternative splicings were found for about 40% of single protein spots. These findings suggested that there exist multiple, but a relatively small number of basic age-related regulatory mechanisms for liver nuclear proteins. These fundamental mechanisms may independently and/or in various combinations function, generating many complex age-related regulatory patterns. Similar studies have also been completed for cytosolic proteins. Analyses on mitochondrial proteins and female liver proteins are under progress. Continued