Mammalian Proteasome Subpopulations with Distinct Molecular Compositions and Proteolytic Activities

作者：Oliver Drews, Robert Wildgruber, Chenggong Zong, Ute Sukop, Mikkel Nissum, Gerhard J. Weber, Aldrin V. Gomes, Peipei Ping · 发表于：Molecular & Cellular Proteomics · 年份：2007 · DOI：10.1074/mcp.m700187-mcp200 · 被引用次数：115 · 研究领域：Ubiquitin and proteasome pathways、Peptidase Inhibition and Analysis、Protease and Inhibitor Mechanisms

The proteasome-dependent protein degradation participates in multiple essential cellular processes. Modulation of proteasomal activities may alter cardiac function and disease phenotypes. However, cardiovascular studies reported thus far have yielded conflicting results. We hypothesized that a contributing factor to the contradicting literature may be caused by existing proteasome heterogeneity in the myocardium. In this investigation, we provide the very first direct demonstration of distinct proteasome subpopulations in murine hearts. The cardiac proteasome subpopulations differ in their molecular compositions and proteolytic activities. Furthermore they were distinguished from proteasome subpopulations identified in murine livers. The study was facilitated by the development of novel protocols for in-solution isoelectric focusing of multiprotein complexes in a laminar flow that support an average resolution of 0.04 pH units. Utilizing these protocols, the majority of cardiac proteasome complexes displayed an isoelectric point of 5.26 with additional subpopulations focusing in the range from pH 5.10 to 5.33. In contrast, the majority of hepatic 20 S proteasomes had a pI of 5.05 and focused from pH 5.01 to 5.29. Importantly proteasome subpopulations degraded specific model peptides with different turnover rates. Among cardiac subpopulations, proteasomes with an approximate pI of 5.21 showed 40% higher trypsin-like activity than those with pI 5.28. Distinct proteasome assembl...