Selective regulation of p38β protein and signaling by integrin-linked kinase mediates bladder cancer cell migration

Abstract

Integrin-linked kinase (ILK) and p38(MAPK) are protein kinases that transduce extracellular signals regulating cell migration and actin cytoskeletal organization. ILK-dependent regulation of p38(MAPK) is critical for mammalian kidney development and in smooth muscle cell migration, however, specific p38 isoforms has not been previously examined in ILK-regulated responses. Signaling by ILK and p38(MAPK) is often dysregulated in bladder cancer, and here we report a strong positive correlation between protein levels of ILK and p38β, which is the predominant isoform found in bladder cancer cells, as well as in patient-matched normal bladder and tumor samples. Knockdown by RNA interference of either p38β or ILK disrupts serum-induced, Rac1-dependent migration and actin cytoskeletal organization in bladder cancer cells. Surprisingly, ILK knockdown causes the selective reduction in p38β cellular protein level, without inhibiting p38β messenger RNA (mRNA) expression. The loss of p38β protein in ILK-depleted cells is partially rescued by the 26S proteasomal inhibitor MG132. Using co-precipitation and bimolecular fluorescent complementation assays, we find that ILK selectively forms cytoplasmic complexes with p38β. In situ proximity ligation assays further demonstrate that serum-stimulated assembly of endogenous ILK-p38β complexes is sensitive to QLT-0267, a small molecule ILK kinase inhibitor. Finally, inhibition of ILK reduces the amplitude and period of serum-induced activation of heat shock protein 27 (Hsp27), a target of p38β implicated in actin cytoskeletal reorganization. Our work identifies Hsp27 as a novel target of ILK-p38β signaling complexes, playing a key role in bladder cancer cell migration.

ATF3 Suppresses Metastasis of Bladder Cancer by Regulating Gelsolin-Mediated Remodeling of the Actin Cytoskeleton

“…The ability of the T24-L to form lung metastases may provide a useful tool in understanding the mechanisms driving metastasis in bladder cancer. Consistent with previously published data and our own work, we used this model to implicate several genes that may be involved in bladder cancer metastasis, such as Src, p38, and ILK (31,39,40). However, ATF3-GSN axis may play an alternative role in mediating bladder cancer metastasis and progression independently of the above-mentioned regulators.…”

Activating Transcription Factor 3 Expression as a Marker of Response to the Histone Deacetylase Inhibitor Pracinostat

“…Upon receiving, lines were expanded and frozen aliquots were made in the first 2 months, and fresh aliquots were thawed before the lines reached 6 months in culture. TSU-Pr1 cells (grade 3) were sourced as described previously (30). The identity of all cell lines was authenticated with STR analysis using AmpFLSTR Identifiler Kit from Applied Biosystems at our MHTP Medical Genomics Facility and confirmed that no cross-contamination was present during this study.…”

Molecular networks underlying myofibroblast fate and fibrosis

“…Conversely, p38 inhibitors block the tension-dependent actin remodeling that is characteristic of myofibroblast transformation. In non-fibroblast cell types, p38 regulates actin polymerization and stress fiber formation, suggesting a global role for p38 in transducing mechanical signals into cytoskeletal changes [111-114]. Taken together, p38 and SRF appear to be the primary integrators of signals from several growth factors and mechanically-activated pathways that drive myofibroblast differentiation ( Figure 2 ).…”