Comparative Proteomic Analysis of a Cytosolic Fraction from β3 Integrin-deficient Cells

Integrins are heterodimeric transmembrane receptors involved in sensing and transmitting informational cues from the extracellular environment to the cell. This study explored sub-proteome changes in response to elimination of the β3 integrin using a knockout murine model. Cleavable isotope-coded affinity tagging (cICAT) in combination with sub-cellular fractionation, multiple dimensions of separation and tandem mass spectrometry (MS/MS) were used to characterize differentially expressed proteins among β3 integrin −/− (β3 −/− ) mouse embryonic fibroblasts and isogenic wild-type (WT) controls. From a cytosolic protein fraction, 48 proteins were identified, in which expression differed by >1.5-fold. Predominant ontological groups included actin-binding/cytoskeletal proteins and protease/protease inhibitors. Interestingly, β3 integrin expression was inversely correlated with expression of cathepsin B, a lysosomal cysteine protease, as its expression was greater by over 3.5-fold in the β3 −/− cells.