Ubiquitylomes Analysis of the Whole blood in Postmenopausal Osteoporosis Patients and healthy Postmenopausal Women.

OBJECTIVES: To determine the mechanisms of ubiquitination in postmenopausal osteoporosis and investigate the ubiquitinated spectrum of novel targets between healthy postmenopausal women and postmenopausal osteoporosis patients, we performed ubiquitylome analysis of the whole blood of postmenopausal women and postmenopausal osteoporosis patients. METHODS: To obtain a more comprehensive understanding of the postmenopausal osteoporosis mechanism, we performed a quantitative assessment of the ubiquitylome in whole blood from seven healthy postmenopausal women and seven postmenopausal osteoporosis patients using high-performance liquid chromatography fractionation, affinity enrichment, and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). To examine the ubiquitylome data, we performed enrichment analysis using an ubiquitylated amino acid motif, Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. RESULTS: Altogether, 133 ubiquitinated sites and 102 proteins were quantified. A difference of more than 1.2 times is considered significant upregulation and less than 0.83 significant downregulation; 32 ubiquitinated sites on 25 proteins were upregulated and 101 ubiquitinated sites on 77 proteins were downregulated. These quantified proteins, both with differently ubiquitinated sites, participated in various cellular processes, such as cellular processes, biological regulation processes, response to stimulus processes, single-organism and metabolic processes. Ubiquitin conjugating enzyme activity and ubiquitin-like protein conjugating enzyme activity were the most highly enriched in molecular function of upregulated sites with corresponding proteins, but they were not enriched in downregulated in sites with corresponding proteins. The KEGG pathways analysis of quantified proteins with differentiated ubiquitinated sites found 13 kinds of molecular interactions and functional pathways, such as glyoxylate and decarboxylate metabolism, dopaminergic synapse, ubiquitin-mediated proteolysis, salivary secretion, coagulation and complement cascades, Parkinson's disease, and hippo signaling pathway. In addition, hsa04120 ubiquitin-mediated proteolysis was the most highly enriched in proteins with upregulated sites, hsa04610 complement and coagulation cascades was the most highly enriched in proteins with downregulated ubiquitinated sites, and hsa04114 Oocyte meiosis was the most highly enriched among all differential proteins. CONCLUSION: Our study expands the understanding of the spectrum of novel targets that are differentially ubiquitinated in whole blood from healthy postmenopausal women and postmenopausal osteoporosis patients. The findings will contribute toward our understanding of the underlying proteostasis pathways in postmenopausal osteoporosis and the potential identification of diagnostic biomarkers in whole blood.

Elevated ubiquitinated proteins in brain and blood of individuals with schizophrenia.

Dysregulation of the ubiquitin proteasome system (UPS) has been linked to schizophrenia but it is not clear if this dysregulation is detectable in both brain and blood. We examined free mono-ubiquitin, ubiquitinated proteins, catalytic ubiquitination, and proteasome activities in frozen postmortem OFC tissue from 76 (38 schizophrenia, 38 control) matched individuals, as well as erythrocytes from 181 living participants, who comprised 30 individuals with recent onset schizophrenia (mean illness duration = 1 year), 63 individuals with 'treatment-resistant' schizophrenia (mean illness duration = 17 years), and 88 age-matched participants without major psychiatric illness. Ubiquitinated protein levels were elevated in postmortem OFC in schizophrenia compared to controls (p = <0.001, AUC = 74.2%). Similarly, individuals with 'treatment-resistant' schizophrenia had higher levels of ubiquitinated proteins in erythrocytes compared to those with recent onset schizophrenia (p < 0.001, AUC = 65.5%) and controls (p < 0.001, AUC = 69.4%). The results could not be better explained by changes in proteasome activity, demographic, medication, or tissue factors. Our results suggest that ubiquitinated protein formation may be abnormal in both the brain and erythrocytes of those with schizophrenia, particularly in the later stages or specific sub-groups of the illness. A derangement in protein ubiquitination may be linked to pathogenesis or neurotoxicity in schizophrenia, and its manifestation in the blood may have prognostic utility.

Potential involvement of ubiquitin-proteasome system dysfunction associated with oxidative stress in the pathogenesis of sickle cell disease.

The ubiquitin-proteasome system (UPS) is an important intracellular proteolytic pathway responsible for the degradation of proteins and oxidative damage; hence it plays a central role in maintaining homeostasis of red blood cells (RBCs). The present study investigated the levels of polyubiquitination, the function of proteasomes and effect of hydroxycarbamide (HC) therapy in RBCs from sickle cell disease (SCD) patients. Polyubiquitinated proteins were found to be elevated in untreated SCD (UT-SCD) patients compared to those in HC-treated SCD patients (HC-SCD) and controls. Activities of ß1 and ß2 subunits were a little higher in UT-SCD patients, and much higher proteolytic activities were observed in all three subunits (ß1, ß2 and ß5) of RBCs in HC-SCD patients compared to those of UT-SCD patients and controls, although the protein levels of these subunits remained approximately the same. It is notable that, despite HC therapy, some patients showed persistent complications and accumulation of polyubiquitinated proteins. The enhanced proteasomal activity among HC-treated patients might remove the polyubiquitinated protein and could be one of the important mechanisms of therapeutic action. These findings could be useful to understand the pathophysiology of SCD and its clinical heterogeneity and identify a suitable therapeutic target for the better management of these patients.