Role Of MFG-E8 Research Articles

PTP1B mediates the inhibitory effect of MFGE8 on insulin signaling through the β5 integrin

Integrins are cell adhesion receptors that dimerize to mediate cell-cell interactions and regulate processes, including proliferation, inflammation, and tissue repair. The role of integrins in regulating insulin signaling is incompletely understood. We have previously shown that binding of the integrin ligand milk fat globule epidermal growth factor like 8 (MFGE8) to the αvβ5 integrin promotes termination of insulin receptor signaling in mice. Upon ligation of MFGE8, integrin β5 complexes with the insulin receptor beta (IRβ) in skeletal muscle, resulting in dephosphorylation of IRβ and reduction of insulin-stimulated glucose uptake. Here, we investigate the mechanism by which the interaction between β5 and IRβ impacts IRβ phosphorylation status. We show in invitro and invivo in skeletal muscle in mice that antibody-mediated blockade of the β5 integrin inhibits and recombinant MFGE8 promotes PTP1B binding to and dephosphorylation of IRβ resulting in increased or reduced insulin-stimulated glucose uptake, respectively. The β5-PTP1B complex is recruited by MFGE8 to IRβ leading to termination of canonical insulin signaling. β5 blockade enhances insulin-stimulated glucose uptake in wildtype but not Ptp1b KO mice indicating that PTP1B functions downstream of MFGE8 in modulating insulin receptor signaling. Furthermore, in a human cohort, we report serum MFGE8 levels correlate with indices of insulin resistance. These data provide mechanistic insights into the role of MFGE8 and β5 in regulating insulin signaling.

Role of Mfge8 in the reduced contractility of diabetic gastroparesis

Coordinated gastric contractility is imperative for ideal digestion and absorption of nutrients. This is impaired during diabetic gastroparesis, a disorder characterized by abnormal gastric smooth muscle contractions leading to delayed gastric emptying. The objective of this research was to further the understanding of the gastric smooth muscle contraction regulatory mechanisms and how these cascades are affected by diabetes. In addition to its anti-inflammatory properties, it has been shown that milk fat globule-epidermal growth factor 8 (Mfge8) binding to ɑ8β1 integrin decreases murine gastric contractile activity by reducing the inhibitory phosphorylation of MLCP, resulting in MLCP activation and reduced myosin phosphorylation. Additionally, Mfge8 is elevated in human serum from type 2 diabetic individuals compared to non-diabetic individuals. It is hypothesized that elevated levels of Mfge8 in smooth muscle tissue will lead to decreased contractility strength, a phenomenon that would resemble gastroparesis secondary to diabetes. We analyzed the contractility and Mfge8 expression of human gastric antrum smooth muscles from obese diabetic and obese non-diabetic individuals who elected to undergo sleeve gastrectomy surgery for weight loss. Short strips of gastric muscle were stimulated to contract with serial concentrations of carbachol and contractile activity was measured with AcqKnowledge software. Mfge8 protein expression was then analyzed using a Wes Simple western instrument. We report that human gastric antrum smooth muscle tissue levels of Mfge8 are elevated in diabetic obese individuals (n=22) compared to non-diabetic obese individuals (n=37, P=0.004). However, we show that the contractile activity of antrum smooth muscle from diabetic obese individuals (n=38) is not dependent on Mfge8 levels and is not significantly different from the contractility of non-diabetic obese individuals (n=38). The rate of contraction, rate of relaxation, and overall tension ( P=0.40) produced by the muscle tissues from the two groups did not significantly differ from each other. It is possible that Mfge8 was not elevated enough to cause reduced contractility, or that those with elevated Mfge8 had not yet developed symptoms of gastroparesis. Mfge8 may serve as a biomarker for diabetic gastroparesis in the future, and additional research is required to determine the pathologic significance of elevated Mfge8 levels in obese diabetic human gastric antrum smooth muscle. This research was supported by a National Institute of Diabetes and Digestive and Kidney Diseases Diabetic Complications Consortium (DiaComp, http://www.diacomp.org ) Grant DK076169, a Takeda Pharmaceuticals Innovation Center Grant to BP, and a UNRSOM Office of Medical Research Grant FD110-PG08935 to DD. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Mfge8 attenuates human gastric antrum smooth muscle contractions

Coordinated gastric smooth muscle contraction is critical for proper digestion and is adversely affected by a number of gastric motility disorders. In this study we report that the secreted protein Mfge8 (milk fat globule-EGF factor 8) inhibits the contractile responses of human gastric antrum muscles to cholinergic stimuli by reducing the inhibitory phosphorylation of the MYPT1 (myosin phosphatase-targeting subunit (1) subunit of MLCP (myosin light chain phosphatase), resulting in reduced LC20 (smooth muscle myosin regulatory light chain (2) phosphorylation. Mfge8 reduced the agonist-induced increase in the F-actin/G-actin ratios of β-actin and γ-actin1. We show that endogenous Mfge8 is bound to its receptor, α8β1 integrin, in human gastric antrum muscles, suggesting that human gastric antrum muscle mechanical responses are regulated by Mfge8. The regulation of gastric antrum smooth muscles by Mfge8 and α8 integrin functions as a brake on gastric antrum mechanical activities. Further studies of the role of Mfge8 and α8 integrin in regulating gastric antrum function will likely reveal additional novel aspects of gastric smooth muscle motility mechanisms.

The significance of tumor cells-derived MFG-E8 in tumor growth of angiosarcoma

BackgroundPrevious studies have indicated that MFG-E8 enhances tumor cell survival, invasion and angiogenesis. However, the role of MFG-E8 in angiosarcoma (AS) has not been clarified. ObjectiveObjective was to elucidate the mechanism of the regulation by MFG-E8 in AS and the association between MFG-E8 and clinicopathological features of AS. MethodsThe effects of the depletion of MFG-E8 by siRNA on tube formation, migration and proliferation in murine AS cells were examined. The effect of administration of anti-MFG-E8 antibody (Ab) on tumor growth of AS in mice was examined. The associations of MFG-E8 expression and clinicopathological features of human AS were assessed. ResultsThe expressions of MFG-E8 in murine and human AS cells were significantly higher than those in melanoma cells, macrophages and endothelial cells. Depletion of MFG-E8 in murine AS cells by siRNA significantly inhibited the formation of capillary-like structures and migration, but not proliferation. Administration of anti-MFG-E8 Ab significantly inhibited tumor growth and decreased the number of tumor-associated macrophages (TAMs) in AS tumors. Tumor size and the number of TAMs in human AS with high expression of MFG-E8 were significantly increased compared to those of AS with low expression of MFG-E8. Progression-free survival and overall survival time of the patients of AS with high expression of MFG-E8 were significantly shorter than those of AS with low expression of MFG-E8. ConclusionsAS-derived MFG-E8 might enhance tumor growth via angiogenesis and the induction of TAMs in autocrine/paracrine manner, and administration of anti-MFG-E8 Ab could be a therapeutic potential for AS.

Inflammatory bone loss associated with MFG-E8 deficiency is rescued by teriparatide.

A prolonged increase in proinflammatory cytokines is associated with osteoporotic and autoimmune bone loss and, conversely, anti-inflammatory pathways are associated with protection against bone loss. Milk fat globule-epidermal growth factor (MFG-E)-8 is a glycoprotein that is proresolving, regulates apoptotic cell clearance, and has been linked to autoimmune disease and skeletal homeostasis. The role of MFG-E8 in the young vs. adult skeleton was determined in mice deficient in MFG-E8 (KO). In vivo, trabecular bone was similar in MFG-E8KO and wild-type (WT) mice at 6 and 16 wk, whereas 22 wk adult MFG-E8KO mice displayed significantly reduced trabecular BV/TV. The number of osteoclasts per bone surface was increased in 22-wk MFG-E8 KO vs. WT mice, and recombinant murine MFG-E8 decreased the number and size of osteoclasts in vitro. Adult MFG-E8KO spleen weight:body weight was increased compared with WT, and flow cytometric analysis showed significantly increased myeloid-derived suppressor cells (CD11bhiGR-1+) and neutrophils (CD11bhiLy6G+) in MFG-E8KO bone marrow, suggesting an inflammatory phenotype. PTH-treated MFG-E8KO mice showed a greater anabolic response (+124% BV/TV) than observed in PTH-treated WT mice (+64% BV/TV). These data give insight into the role of MFG-E8 in the adult skeleton and suggest that anabolic PTH may be a valuable therapeutic approach for autoimmune-associated skeletal disease.-Michalski, M. N., Seydel, A. L., Siismets, E. M., Zweifler, L. E., Koh, A. J., Sinder, B. P., Aguirre, J. I., Atabai, K., Roca, H., McCauley, L. K. Inflammatory bone loss associated with MFG-E8 deficiency is rescued by teriparatide.

皮膚創傷治癒による分泌蛋白質 MFG-E8 の役割：MFG-E8 と塩基性線維芽細胞増殖因子（bFGF）による創傷治癒効果の検討

皮膚創傷治癒による分泌蛋白質 MFG-E8 の役割：MFG-E8 と塩基性線維芽細胞増殖因子（bFGF）による創傷治癒効果の検討

Role of MFG-E8 in skin wound healing

Role of MFG-E8 in skin wound healing

SOCS3 Promotes the Activation of CCR2-Dependent Migratory Cd11b+GR-1lowly6chigh Macrophages in Murine Cerulein Pancreatitis

mice followed by comparison of MFG-E8+/+ and MFG-E8-/mice for pathological changes in the pancreas. Typically, MFG-E8+/+ and MFG-E8-/mice (7 weeks, male) were subjected to ten injections of cerulein (50 μg/kg, i.p.) at hourly intervals. They were sacrificed at various time points after the final cerulein administration. We found that MFG-E8 deficiency did not affect the severity of acute phase of cerulein-induced pancreatitis. However, pancreatic recovery following cerulein-induced pancreatitis was markedly delayed in MFG-E8-/mice comparing to wild-type controls. Furthermore, we examined whether lack of MFG-E8 leads to progression of recurrent pancreatic injury to chronic inflammation. Briefly, MFG-E8-/and MFG-E8+/+ mice were respectively subjected to repeated courses of acute pancreatitis for two weeks. Control mice were treated with saline. Using histological examination, we revealed that wild-type mice recovered from repeated acute pancreatitis within 7 days after the final cerulein administration. In contrast, pancreas from MFG-E8-/displayed persistent inflammatory cell infiltration, disruption of acinar cells, and replacement of parenchymal tissues with collagen fibers and stromal cells. Together, the data suggest a central role for MFG-E8 in pancreatic recovery from pancreatitis. In conclusion, MFG-E8 deficiency impairs pancreatic recovery. This novel finding may provide a potential therapeutic target in the further development of novel molecular agents for patients with pancreatitis and pancreatic fibrosis.

P3-359: The role of MFG-E8 in glial-neuronal interactions and neuroinflammation

P3-359: The role of MFG-E8 in glial-neuronal interactions and neuroinflammation

Weaning-induced expression of a milk-fat globule protein, MFG-E8, in mouse mammary glands, as demonstrated by the analyses of its mRNA, protein and phosphatidylserine-binding activity.

A milk membrane glycoprotein, MFG-E8 [milk fat globule-EGF (epidermal growth factor) factor 8], is expressed abundantly in lactating mammary glands in stage- and tissue-specific manners, and has been believed to be secreted in association with milk fat globules. In the present paper, we describe further up-regulation of MFG-E8 in involuting mammary glands, where the glands undergo a substantial increase in the rate of epithelial cell apoptosis, and a possible role of MFG-E8 in mediating recognition and engulfment of apoptotic cells through its specific binding to PS (phosphatidylserine). Immunoblotting and RNA blotting analyses revealed that both MFG-E8 protein and MFG-E8 mRNA were markedly increased in mammary tissue within 3 days of either natural or forced weaning (pup withdrawal) of lactating mice. Using immunohistochemical analysis of the mammary tissue cryosections, the MFG-E8 signal was detected around the epithelium of such involuting mammary glands, but was almost undetectable at early- and mid-lactation stages, although strong signals were obtained for milk fat globules stored in the alveolar lumen. Some signals double positive to a macrophage differentiation marker, CD68, and MFG-E8 were detected in the post-weaning mammary tissue, although such double-positive signals were much smaller in number than the MFG-E8 single-positive ones. Total MFG-E8 in milk was also increased in the post-weaning mammary glands and, furthermore, the free MFG-E8 content in the post-weaning milk, as measured by in vitro PS-binding and apoptotic HC11 cell-binding activities, was much higher than that of lactation. In addition, the post-weaning milk enhanced the binding of apoptotic HC11 cells to J774 macrophages. Sucrose density-gradient ultracentrifugation analyses revealed that such enhanced PS-binding activity of MFG-E8 was present in membrane vesicle fractions (density 1.05-1.13 g/ml), rather than milk fat globule fractions. The weaning-induced MFG-E8 might play an important role in the recognition and engulfment of apoptotic epithelial cells by the neighbouring phagocytic epithelial cells in involuting mammary glands.