Detection of Membranous Protein Alterations on BCG-activated Macrophages Involved in Contact-dependent Tumoricidal Processes

Abstract

Activated macrophages possess tumoricidal ability associated with a cell-cell contact mechanism. However, the nature of the cell surface proteins involved in this tumoricidal process is not yet known. In this research, macrophages activated by bacterium Mycobacterium bovis bacillus Calmette-Guerin (BCG) and by thioglycolate (TGC) were chosen as two comparative models for the large-scale detection of cell surface protein alterations involved in this process. A proteomics approach involving SDS-PAGE followed by LC-MS/MS was used to characterize membrane proteins of the two models. A total of 421 uniquely expressed proteins were identified on the BCG-activated macrophage membrane. Functional groups indicating signal transduction, transport, and cell adhesion, among others, were significantly enriched in this group of proteins. In addition, 42 proteins associated with the plasma membrane were detected. These membrane proteins may contact tumor cells directly and play important roles in the tumoricidal process. In general, this study provides an initial database of candidate proteins that can now be screened as potential regulators of the adherence-dependent tumoricidal properties associated with macrophages.