Active Stress Kinases in Proliferating Endothelial Cells Associated with Cytoskeletal Structures

Abstract

It has become increasingly clear that stress-activated protein kinases have cytoplasmic substrates in addition to well-established transcription factor substrates in cell nuclei. The present study documented specific cytoplasmic locations of these enzymes in proliferating vascular cells. Immunofluorescent staining for active c-jun NH2-terminal kinase (JNK), the precipitation of JNK with microfilaments, and the loss of fiber-associated active JNK after cytochalasin treatment, but not nocodazole treatment, together indicate that active JNK is associated with stress fibers. The lack of complete scaffold colocalization and the total lack of immediate upsteam kinase colocalization along with the inability of JNK inhibitors to alter JNK-microfilament associations suggest that the microfilament association is not simply involved in enzyme activation. In addition, active p38 was found along with vinculin in focal adhesions. Although the p38 in focal adhesions could also be disrupted by cytochalasin treatment, it remained stable after nocodazole treatment. These results support the hypothesis that vascular cell stress kinase enzymes are important for signal transduction in the cytoplasm. The localization of active stress-activated protein kinases to specific cytoskeletal structures in proliferating cells suggests that subsets of these enzymes are involved in signal transduction to and/or from the cytoskeleton under conditions that include vascular cell proliferation.

Hydrostatic pressure promotes the proliferation and osteogenic/chondrogenic differentiation of mesenchymal stem cells: The roles of RhoA and Rac1

“…These results, for the first time, confirmed that the activation of the JNK pathway by hydrostatic pressure may be negatively regulated by RhoA and Rac1. Previous studies have shown that there were associations between active phosphorylated JNK and stress fibers in cells (Hamel et al, 2006;Yang et al, 2007). Furthermore, a proximity ligation assay demonstrated the co-localization of phospho-JNK and F-actin under mechanical stimulation (Mengistu et al, 2011).…”

Heparin Decreases in Tumor Necrosis Factor α (TNFα)-induced Endothelial Stress Responses Require Transmembrane Protein 184A and Induction of Dual Specificity Phosphatase 1

“…Reorganization of F-actin into stress fibers through the MAPK signaling cascades in response to TNF␣ and low or disturbed fluid shear stress has also been shown to increase EC permeability (39,41,42). JNK associates with stress fibers in ECs and plays a role in actin remodeling (43,44). Regions of the vasculature with disturbed flow have higher levels of active JNK (45,46).…”

MST Kinases Monitor Actin Cytoskeletal Integrity and Signal via c-Jun N-Terminal Kinase Stress-Activated Kinase To Regulate p21Waf1/Cip1 Stability

“…Active JNK has been found in association with F-actin (29), where it may contribute to regulating actin polymerization and remodelling (4). Although in Saccharomyces cerevisiae the MAP3K Ssk2p contributes to actin recovery following osmotic stress, this process is not mediated via the Hog1 SAPK pathway but instead results from the association of Ssk2p with the polarisome complex and the formin protein Bni1p to mediate polarized actin polymerization (8).…”