The removal of albumin and other high abundance proteins is a routine first step in the analysis of serum and plasma proteomes. However, as albumin can bind proteins and peptides, there is a universal concern as to how the serum proteome is changed by the removal of albumin. To address this concern, the current study was designed to identify proteins and peptides removed from the serum during albumin depletion; to determine which of these are bound to albumin (rather than copurified) and whether the bound proteins are intact proteins or peptide fragments. Sequential, independent analyses including both anti-albumin antibody (anti-HSA) affinity chromatography and SEC were used to isolate albumin-bound proteins. RP-HPLC and 1-D SDS-PAGE were then used to further separate the proteins prior to identification by MS/MS. Finally, whole protein molecular weight (MW) MS measurements coupled with protein coverage obtained by MS were combined to assess whether the bound proteins were intact or peptide fragments. Combining the results from multiple approaches, 35 proteins, of which 24 are intact, were found to be associated with albumin, and they include both known high and low abundance proteins.

Summary Background During cytokinesis, regulatory signals are presumed to emanate from the mitotic spindle. However, what these signals are and how they lead to the spatiotemporal changes in the cortex structure, mechanics, and regional contractility are not well understood in any system. Results To investigate pathways that link the microtubule network to the cortical changes that promote cytokinesis, we used chemical genetics in Dictyostelium to identify genetic suppressors of nocodazole, a microtubule depolymerizer. We identified 14-3-3 and found that it is enriched in the cortex, helps maintain steady state microtubule length, contributes to normal cortical tension, modulates actin wave formation, and controls the symmetry and kinetics of cleavage furrow contractility during cytokinesis. Furthermore, 14-3-3 acts downstream of a Rac small GTPase (RacE), associates with myosin II heavy chain and is needed to promote myosin II bipolar thick filament remodeling. Conclusion 14-3-3 connects microtubules, Rac and myosin II to control several aspects of cortical dynamics, mechanics, and cytokinesis cell shape change. Further, 14-3-3 interacts directly with myosin II heavy chain to promote bipolar thick filament remodeling and distribution. Overall, 14-3-3 appears to integrate several critical cytoskeletal elements that drive two important processes cytokinesis shape change and cell mechanics.

Background-Prostate specific antigen (PSA) is the best-known member of the kallikreinrelated peptidase family, with an established role as a prostatic disease biomarker. Although it is produced at high levels by all stages of prostate cancer, it is uncertain if PSA plays a role in prostate cancer initiation and progression. We decided to investigate the impact of PSA and its enzymatic activity on tumor cell growth rates.