Focal adhesions and Ras are functionally and spatially integrated to mediate IL-1 activation of ERK

Increased IL-1α expression is correlated with bladder cancer malignant progression

INTRODUCTION

To explore the function of interleukin 1α (IL-1α) in bladder cancer (BCa).

MATERIAL AND METHODS

Immunohistochemistry (IHC) was used to test the protein expression of IL-1α in BCa tissues. The relationship between IL-1α and clinical characteristics was analyzed by the Kaplan-Meier curve method. The gene and protein expression was tested by reverse transcription quantitative polymerase chain reaction (RT-q-PCR) and western blot, respectively. Colony formation and MTT assays were used to detect the potential of proliferation in vitro, and scratch and transwell chamber assays were used to detect the potential of invasion in vitro. Markers of proliferation such as Ki-67 and proliferating cell nuclear antigen (PCNA) and markers of invasion such as MMP-2 and MMP-9 were detected by western blot. Xenograft study was used for the in vivo experiment.

RESULTS

We found that IL-1α was highly expressed in BCa patients while highly expressed IL-1α was significantly related to short overall survival and progression-free survival in BCa as well. Moreover, knockdown of IL-1α might inhibit the ability of cancer cells to proliferate and invade or migrate both in vitro and in vivo.

CONCLUSIONS

Our findings suggested that IL-1α might be a therapy target for BCa malignant progression.

Short term exposure of beta cells to low concentrations of interleukin-1β improves insulin secretion through focal adhesion and actin remodeling and regulation of gene expression

Type 2 diabetes involves defective insulin secretion with islet inflammation governed in part by IL-1β. Prolonged exposure of islets to high concentrations of IL-1β (>24 h, 20 ng/ml) impairs beta cell function and survival. Conversely, exposure to lower concentrations of IL-1β for >24 h improves these same parameters. The impact on insulin secretion of shorter exposure times to IL-1β and the underlying molecular mechanisms are poorly understood and were the focus of this study. Treatment of rat primary beta cells, as well as rat or human whole islets, with 0.1 ng/ml IL-1β for 2 h increased glucose-stimulated (but not basal) insulin secretion, whereas 20 ng/ml was without effect. Similar differential effects of IL-1β depending on concentration were observed after 15 min of KCl stimulation but were prevented by diazoxide. Studies on sorted rat beta cells indicated that the enhancement of stimulated secretion by 0.1 ng/ml IL-1β was mediated by the NF-κB pathway and c-JUN/JNK pathway acting in parallel to elicit focal adhesion remodeling and the phosphorylation of paxillin independently of upstream regulation by focal adhesion kinase. Because the beneficial effect of IL-1β was dependent in part upon transcription, gene expression was analyzed by RNAseq. There were 18 genes regulated uniquely by 0.1 but not 20 ng/ml IL-1β, which are mostly involved in transcription and apoptosis. These results indicate that 2 h of exposure of beta cells to a low but not a high concentration of IL-1β enhances glucose-stimulated insulin secretion through focal adhesion and actin remodeling, as well as modulation of gene expression.

Inelastic behaviour of collagen networks in cell-matrix interactions and mechanosensation

The mechanical properties of extracellular matrix proteins strongly influence cell-induced tension in the matrix, which in turn influences cell function. Despite progress on the impact of elastic behaviour of matrix proteins on cell-matrix interactions, little is known about the influence of inelastic behaviour, especially at the large and slow deformations that characterize cell-induced matrix remodelling. We found that collagen matrices exhibit deformation rate-dependent behaviour, which leads to a transition from pronounced elastic behaviour at fast deformations to substantially inelastic behaviour at slow deformations (1 μm min(-1), similar to cell-mediated deformation). With slow deformations, the inelastic behaviour of floating gels was sensitive to collagen concentration, whereas attached gels exhibited similar inelastic behaviour independent of collagen concentration. The presence of an underlying rigid support had a similar effect on cell-matrix interactions: cell-induced deformation and remodelling were similar on 1 or 3 mg ml(-1) attached collagen gels while deformations were two- to fourfold smaller in floating gels of high compared with low collagen concentration. In cross-linked collagen matrices, which did not exhibit inelastic behaviour, cells did not respond to the presence of the underlying rigid foundation. These data indicate that at the slow rates of collagen compaction generated by fibroblasts, the inelastic responses of collagen gels, which are influenced by collagen concentration and the presence of an underlying rigid foundation, are important determinants of cell-matrix interactions and mechanosensation.

Ras-guanine-nucleotide-releasing factors 1 and 2 interact with PLCγ at focal adhesions to enable IL-1-induced Ca(2+) signalling, ERK activation and MMP-3 expression

IL (interleukin)-1 signalling in anchorage-dependent cells involves focal-adhesion-restricted and Ca2+-dependent Ras and ERK (extracellular-signal-regulated kinase) activation that leads to MMP (matrix metalloproteinase) release and extracellular matrix remodelling. Ras activity is regulated, in part, by the Ca2+-responsive Ras GRFs (guanine-nucleotide-releasing factors) 1 and 2, but the mechanisms that link and localize IL-1-induced Ca2+ signalling to focal adhesions are not defined. In the present study we characterized the role of Ras-GRF1/2 in Ca2+ and Ras→ERK signalling after IL-1 stimulation. By immunoprecipitation we found that Ras-GRF1/2 associates with PLCγ1 (phospholipase Cγ1). This association enables PLCγ1 recruitment to focal adhesions and is required for Ras signalling, ERK activation and MMP-3 release downstream of IL-1 stimulation. Depletion of PLCγ1 by siRNA (small interfering RNA) abolished IL-1-induced Ras activation and MMP-3 expression. Buffering of cytosolic Ca2+ reduced Ras interactions with Ras-GRF1/2 and blocked MMP-3 release. The results of the present study show that, in addition to their functions as Ras-exchange factors, Ras-GRF1 and -GRF2 may act as adaptors that bind PLCγ1 and restrict Ca2+ signalling to the vicinity of focal adhesions, indicating a new role for these GRFs that is required for IL-1 induction of the Ras→ERK pathway and MMP-3 expression.

IL-1β enhances cell adhesion to degraded fibronectin

IL-1β is a prominent proinflammatory cytokine that mediates degradation of extracellular matrix proteins through increased expression of matrix metalloproteinases, which involves a signaling pathway in adherent cells that is restricted by focal adhesions. Currently, the mechanism by which IL-1β affects cell adhesion to matrix proteins is not defined, and it is not known whether degraded matrix proteins affect IL-1β signaling. We examined adhesion-related IL-1β signaling in fibroblasts attaching to native or MMP3-degraded fibronectin. IL-1β increased cell attachment, resistance to shear force and the numbers of focal adhesions containing activated β(1) integrins. IL-1β-enhanced attachment required FAK, kindlins 1/2, and talin. MMP3-degraded fibronectin-inhibited IL-1β-enhanced cell adhesion and promoted spontaneous ERK activation that was independent of IL-1β treatment. We conclude that IL-1β enhances the adhesion of anchorage-dependent cells to MMP3-degraded fibronectin, which, in turn, is associated with deregulated cellular responses to IL-1β. These data point to a novel role of IL-1β as a proadhesive signaling molecule in inflammation that employs kindlins and talin to regulate adhesion.