ABSTRACT
Receptor tyrosine phosphatase sigma (RPTPσ) plays an important role in the regulation of axonal outgrowth and neural regeneration. Recent studies have identified two RPTPσ ligands, chondroitin sulfate proteoglycans (CSPGs) and heparan sulfate proteoglycans (HSPG), which can modulate RPTPσ activity by affecting its dimerization status. Here, we developed a split luciferase assay to monitor RPTPσ dimerization in living cells. Using this system, we demonstrate that heparin, an analog of heparan sulfate, induced the dimerization of RPTPσ, whereas chondroitin sulfate increased RPTPσ activity by inhibiting RPTPσ dimerization. Also, we generated several novel RPTPσ IgG monoclonal antibodies, to identify one that modulates its activity by inducing/stabilizing dimerization in living cells. Lastly, we demonstrate that this antibody promotes neurite outgrowth in SH-SY5Y cells. In summary, we demonstrated that the split luciferase RPTPσ activity assay is a novel high-throughput approach for discovering novel RPTPσ modulators that can promote axonal outgrowth and neural regeneration.
Subject(s)
Antibodies/immunology , Receptor-Like Protein Tyrosine Phosphatases/immunology , Animals , Axons , Cell Line , Humans , Mice , Native Polyacrylamide Gel ElectrophoresisABSTRACT
BACKGROUND & AIMS: Despite the descriptive presence of cancer cachexia (CC) in clinical practice, the underlying mechanisms and diagnostic definition have not been clearly identified. Recent work, attempting to establish diagnostic and staging criteria for CC, has identified IL-6 as a biomarker. This study aimed to investigate the clinical relevance of plasma levels of four pro-inflammatory cytokines (IL-6, IL-1ß, IL-8 and TNF-α) in advanced cancer patients (ACP) to further establish their potential in the diagnostic definition of CC. METHODS: Blood was obtained from 83 ACP (47 male and 36 female, aged 34-85 years) and analyzed for white blood cells, lymphocytes, C-reactive protein, albumin and cytokines. Subjects completed questionnaires to establish weakness, loss of appetite, fatigue, quality of life and weight loss; completed tests to determine strength, body composition and sarcopenia; and consented to chart review to calculate survival and total days admitted to hospital. RESULTS: This study shows that, in ACP, IL-1ß is better associated with clinical features of the cachectic condition, such as weakness, loss of appetite, weight loss and sarcopenia, than IL-6. CONCLUSION: IL-6 may not best represent the clinical correlates of CC in ACP. Additional cytokines should be considered in the definition of this condition.
