Macrophage activation increases the invasive properties of hepatoma cells by destabilization of the adherens junction

AbstractTumor-associated macrophages play an important role in tumor progression, but whether they exert a tumor-progressive effect remains controversial. Here, we demonstrated that activated macrophage-conditioned medium (AMCM) obtained from RAW macrophages (RAW/AMCM) induced epithelial-mesenchymal transition (EMT) and stimulated the migratory and invasive activities of HepG2 cells, whereas control conditioned media had no effect. Epithelial-cadherin (E-cadherin) and β-catenin staining patterns were altered at the adherens junctions by RAW/AMCM treatment, with an approximately 50% decrease in E-cadherin and β-catenin in the cell membrane. Importantly, levels of β-catenin-associated E-cadherin were also decreased. Following RAW/AMCM treatment, enhanced activation of c-Src was seen prior to increased tyrosine phosphorylation of β-catenin, and this led to the destabilization of adherens junctions. Pretreatment of HepG2 cells with the Src kinase inhibitor, PP2, completely abolished the effects of RAW/AMCM on the EMT, migration, invasion, and expression and association of E-cadherin and β-catenin. AMCMs obtained from human THP-1 monocytes and mouse peritoneal macrophages also caused disassembly of the adherens junctions and migration of HepG2 cells. Furthermore, inhibition of the epidermal growth factor receptor (EGFR) with gefitinib partially prevented the downregulation of E-cadherin and β-catenin at the adherens junctions and migration behavior induced by RAW/AMCM. Our results suggest that activated macrophages have a tumor-progressive effect on HepG2 cells which involves the c-Src- and EGFR-dependent signaling cascades

A lipid droplet-specific capsule is present in rat adrenal cells: evidence from a monoclonal antibody

　　 We have used a monoclonal antibody, A2, to study the structure and function on the lipid droplet capsule in steroidogenic adrenal cells . This antibody reacts with a 160-kD protein found in the rat adrenal cortex. Immunofluorescence microscopy shows a dominant rim pattern, which surrounds individual lipid droplets and is distinct from the filamentous vimentin staining. The boundary of lipid droplets in steroidgenic Leydig cells and 3T3 adipocytes is also immunostained by this antibody . The strong association of the 160-kD protein with the lipid droplet demonstrated by its resistance to Triton X- 100 extraction. Stimulation of steroid secretion by adrenocorticotropin results in the detachment of this protein from the lipid droplet and its movement to the cytosol. These findings suggest that the translocation of this 160-kD protein from lipid droplet surface to cytosol on stimulation might be important in facilitating the binding of cholesterol ester hydrolase to the surface of lipid droplet, as proposed for adipocytes, during lipolytic stimulation.#1490

Role of desmin filaments in chicken cardiac myofibrillogenesis

Desmin filaments are muscle-specific intermediate filaments located at the periphery of the Z-discs, and they have been postulated to play a critical role in the lateral registration of myofibrils. Previous studies suggest that intermediate filaments may be involved in titin assembly during the early stages of myofibrillogenesis. In order to investigate the putative function of desmin filaments in myofibrillogenesis, rabbit anti- desmin antibodies were introduced into cultured cardiomyocytes by electroporation to perturb the normal function of desmin filaments. Changes in the assembly of several sarcomeric proteins were examined by immunofluorescence. In cardiomyocytes incorporated with normal rabbit serum, staining for -actinin and muscle actin displayed the typical Z-line and I-band patterns, respectively, while staining for titin with monoclonal anti- titin A12 antibody, which labels a titin epitope at the A -I junction, showed the periodic doublet staining pattern. Staining for C- protein gave an amorphous pattern in early cultures and identified A-band doublets in older cultures. In contrast, in cardiomyocytes incorporated with anti-desmin antibodies, -actinin was found in disoriented Z-discs and the myofibrils became fragmented, forming mini-sarcomeres. In addition, titin was not organized into the typical A-band doublet, but appeared to be aggregated. Muscle actin staining was especially weak and appeared in tiny clusters. Moreover, in all ages of cardiomyocytes tested, C-protein remained in the disassembled form. The present data suggest the essential role of desmin in myofibril assembly