A rapid one-step extraction procedure for the isolation of ubiquitin from human erythrocytes for antibody production

Motor protein function in skeletal abdominal muscle of cachectic cancer patients

Cachexia presents with ongoing muscle wasting, altering quality of life in cancer patients. Cachexia is a limiting prognostic factor for patient survival and health care costs. Although animal models and human trials have shown mechanisms of motorprotein proteolysis, not much is known about intrinsic changes of muscle functionality in cancer patients suffering from muscle cachexia, and deeper insights into cachexia pathology in humans are needed. To address this question, rectus abdominis muscle samples were collected from several surgical control, non-cachectic and cachectic cancer patients and processed for skinned fibre biomechanics, molecular in vitro motility assays, myosin isoform protein compositions and quantitative ubiquitin polymer protein analysis. In pre-cachectic and cachectic cancer patient samples, maximum force was significantly compromised compared with controls, but showed an unexpected increase in myofibrillar Ca²⁺ sensitivity consistent with a shift from slow to fast myosin isoform expression seen in SDS-PAGE analysis and in vitro motility assays. Force deficit was specific for ‘cancer’, but not linked to presence of cachexia. Interestingly, quantitative ubiquitin immunoassays revealed no major changes in static ubiquitin polymer protein profiles, whether cachexia was present or not and were shown to mirror profiles in control patients. Our study on muscle function in cachectic patients shows that abdominal wall skeletal muscle in cancer cachexia shows signs of weakness that can be partially attributed to intrinsic changes to contractile motorprotein function. On protein levels, static ubiquitin polymeric distributions were unaltered, pointing towards evenly up-regulated ubiquitin protein turnover with respect to ubiquitin conjugation, proteasome degradation and de-ubiquitination.

Extracellular ubiquitin: immune modulator and endogenous opponent of damage-associated molecular pattern molecules

Ubiquitin is a post-translational protein modifier and plays essential roles in all aspects of biology. Although the discovery of ubiquitin introduced this highly conserved protein as a molecule with extracellular actions, the identification of ubiquitin as the ATP-dependent proteolysis factor 1 has focused subsequent research on its important intracellular functions. Little attention has since been paid to its role outside of the cell. During recent years, multiple observations suggest that extracellular ubiquitin can modulate immune responses and that exogenous ubiquitin has therapeutic potential to attenuate exuberant inflammation and organ injury. These observations have not been integrated into a comprehensive assessment of its possible role as an endogenous immune modulator. This review recapitulates the current knowledge about extracellular ubiquitin and discusses an emerging facet of its role in biology during infectious and noninfectious inflammation. The synopsis of these data along with the recent identification of ubiquitin as a CXCR4 agonist suggest that extracellular ubiquitin may have pleiotropic roles in the immune system and functions as an endogenous opponent of DAMPs. Functions of extracellular ubiquitin could constitute an evolutionary conserved control mechanism aimed to balance the immune response and prevent exuberant inflammation. Further characterization of its mechanism of action and cellular signaling pathways is expected to provide novel insights into the regulation of the innate immune response and opportunities for therapeutic interventions.

Comparison of methods for the in vitro assembly of postmortem human brain microtubules that retain the microtubule-associated protein tau

Several methods for the in vitro assembly of microtubules from postmortem human brain were compared for the purpose of obtaining microtubule preparations that best retained their microtubule-associated proteins. The polymerized microtubules from the preparations were examined by negative staining and electron microscopy and shown to consist of well-formed microtubules with varying amounts of abnormal assembly products that differed between methods. The microtubule protein was analyzed by SDS-polyacrylamide gel electrophoresis, quantitative densitometry, as well as trans-blotted onto membranes which were reacted with monoclonal antibodies to tubulin subunits and microtubule-associated proteins. All the preparations were found to contain both the alpha- and beta-tubulin subunits with quantitative differences, but they varied most, both quantitatively and qualitatively, in their content of microtubule-associated proteins. The optimal method for the assembly of soluble tubulin from postmortem human brain cytosol into intact microtubules which specifically retained most of their MAPs, especially tau, employed 4 M glycerol assembly buffer in the presence of 10 microM taxol and 1 mM GTP. The isolation methods were used to compare young and aged brains, and there were fewer microtubule-associated proteins, especially tau, associated with the microtubules in advanced age, in all preparations.