The proteome of any system is a dynamic entity, such that the intracellular concentration of a protein is dictated by the relative rates of synthesis and degradation. In this work, we have analyzed time-dependent changes in the incorporation of a stable amino acid resolved precursor, a protocol we refer to as "dynamic SILAC", using 1-D gel separation followed by in-gel digestion and LC-MS/MS analyses to profile the intracellular stability of almost 600 proteins from human A549 adenocarcinoma cells, requiring multiple measures of the extent of labeling with stable isotope labeled amino acids in a classic label-chase experiment. As turnover rates are acquired, a profile can be built up that allows exploration of the 'dynamic proteome' and of putative features that predispose a protein to a high or a low rate of turnover. Moreover, measurement of the turnover rate of individual components of supramolecular complexes provides a unique insight in processes of protein complex assembly and turnover.

CYK4 activity as a GTPase-activating protein is required during anaphase to inhibit Rac1-dependent effector pathways associated with control of cell spreading and adhesion.

The ligand-dependent degradation of activated tyrosine kinase receptors provides a means by which mitogenic signalling can be attenuated. In many cell types the ligand-dependent degradation of the tyrosine kinase receptor Met is completely dependent on the activity of the 26S proteasome (Je ers et al., 1997b). We now show that degradation also requires tra cking to late endosomal compartments and the activity of acid dependent proteases as determined by the e ects of a dominant negative form of dynamin (K44A) and a vacuolar-ATPase inhibitor, concanamycin. We show that in the presence of the proteasome inhibitor lactacystin, Met fails to redistribute from the plasma membrane to intracellular compartments. This observation is most consistent with the interpretation that proteasome activity is required for Met internalization and only indirectly for its degradation. Oncogene (2001) 20, 2761 ± 2770.

The asymmetric cortical localization of dynein during spindle orientation requires dynein light chain 1 and a spindle-microtubule–associated adaptor formed by CHIA and HMMR.