Protein tyrosine phosphatase 1B targets focal adhesion kinase and paxillin in cell-matrix adhesions

Focal adhesion kinase (FAK): emerging target for drug-resistant malignant tumors

Malignant tumors associated with drug resistance present a significant challenge for clinicians and drug developers. Mutations and alterations within the tumor microenvironment frequently drive cancer cell invasion and metastasis. Despite identifying numerous molecular targets and lead compounds, achieving sustained efficacy remains challenging due to the rapid mutation rates and the emergence of resistance. Recently, Focal Adhesion Kinase (FAK), a non-receptor tyrosine kinase, has emerged as a promising target for inhibiting cancer progression, with several lead molecules advancing through clinical trials. FAK plays a critical role in cancer pathology by regulating cell adhesion, migration, proliferation, and survival. Its structure comprises three domains- the N-terminal FERM domain, kinase domain, and C-terminal focal adhesion targeting domain- contributing to its functional versatility. Ligands targeting the FERM and kinase domains can suppress cancer cell proliferation, invasion, and migration. The FERM domain, a member of the ezrin, radixin, and moesin family, is particularly noteworthy for its ligand-binding capabilities and potential to inhibit tumor growth. While FAK is a compelling anticancer target, challenges such as tissue-specific physiological variability and broad ligand specificity remain. This review provides a detailed analysis of FAK's role in cancer progression and explores emerging molecules targeting FAK as potential treatments for drug-resistant malignant tumors.

The emerging roles of the endoplasmic reticulum in mechanosensing and mechanotransduction

Cells are continuously subjected to physical and chemical cues from the extracellular environment, and sense and respond to mechanical cues via mechanosensation and mechanotransduction. Although the role of the cytoskeleton in these processes is well known, the contribution of intracellular membranes has been long neglected. Recently, it has become evident that various organelles play active roles in both mechanosensing and mechanotransduction. In this Review, we focus on mechanosensitive roles of the endoplasmic reticulum (ER), the functions of which are crucial for maintaining cell homeostasis. We discuss the effects of mechanical stimuli on interactions between the ER, the cytoskeleton and other organelles; the role of the ER in intracellular Ca2+ signalling via mechanosensitive channels; and how the unfolded protein response and lipid homeostasis contribute to mechanosensing. The expansive structure of the ER positions it as a key intracellular communication hub, and we additionally explore how this may be leveraged to transduce mechanical signals around the cell. By synthesising current knowledge, we aim to shed light on the emerging roles of the ER in cellular mechanosensing and mechanotransduction.

Cell-Material Interplay in Focal Adhesion Points

The complex interplay between cells and materials is a key focus of this research, aiming to develop optimal scaffolds for regenerative medicine. The need for tissue regeneration underscores understanding cellular behavior on scaffolds, especially cell adhesion to polymer fibers forming focal adhesions. Key proteins, paxillin and vinculin, regulate cell signaling, migration, and mechanotransduction in response to the extracellular environment. This study utilizes advanced microscopy, specifically the AiryScan technique, along with advanced image analysis employing the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) cluster algorithm, to investigate protein distribution during osteoblast cell adhesion to polymer fibers and glass substrates. During cell attachment to both glass and polymer fibers, a noticeable shift in the local maxima of paxillin and vinculin signals is observed at the adhesion sites. The focal adhesion sites on polymer fibers are smaller and elliptical but exhibit higher protein density than on the typical glass surface. The characteristics of focal adhesions, influenced by paxillin and vinculin, such as size and density, can potentially reflect the strength and stability of cell adhesion. Efficient adhesion correlates with well-organized, larger focal adhesions characterized by increased accumulation of paxillin and vinculin. These findings offer promising implications for enhancing scaffold design, evaluating adhesion to various substrates, and refining cellular interactions in biomedical applications.