Paxillin mutations affect focal adhesions and lead to altered mitochondrial dynamics

Abstract

Cytoskeletal and focal adhesion abnormalities are observed in several types of cancer, including lung cancer. We have previously reported that paxillin (PXN) was mutated, amplified, and overexpressed in a significant number of lung cancer patient samples, that PXN protein was upregulated in more advanced stages of lung cancer compared with lower stages, and that the PXN gene was also amplified in some pre-neoplastic lung lesions. Among the mutations investigated, we previously found that PXN variant A127T in lung cancer cells enhanced cell proliferation and focal adhesion formation and colocalized with the anti-apoptotic protein B Cell Lymphoma 2 (BCL-2), which is known to localize to the mitochondria, among other sites. To further explore the effects of activating mutations of PXN on mitochondrial function, we cloned and expressed wild-type PXN and variants containing the most commonly occurring PXN mutations (P46S, P52L, G105D, A127T, P233L, T255I, D399N, E423K, P487L, and K506R) in a GFP-tagged vector using HEK-293 human embryonic kidney cells. Utilizing live-cell imaging to systematically study the effects of wild-type PXN vs. mutants, we created a model that recapitulates the salient features of the measured dynamics and conclude that compared with wild-type, some mutant clones confer enhanced focal adhesion and lamellipodia formation (A127T, P233L, and P487L) and some confer increased association with BCL-2, Dynamin-related Protein-1 (DRP-1), and Mitofusion-2 (MFN-2) proteins (P233L and D399N). Further, PXN mutants, through their interactions with BCL-2 and DRP-1, could regulate cisplatin drug resistance in human lung cancer cells. The data reported herein suggest that mutant PXN variants play a prominent role in mitochondrial dynamics with direct implications on lung cancer progression and hence, deserve further exploration as therapeutic targets.

Metabolic and Phenotypic Characterization of Human Skin Fibroblasts After Forcing Oxidative Capacity

“…kidney epithelial cells, HEK-293 (Kawada et al, 2013). For the same cell line, it was also shown that paxillin mutations induced cell survival advantage and co-localized with the antiapoptotic protein Bcl-2 (Kawada et al, 2013). We can postulate that the increased expression of paxillin was induced by forcing oxidative capacity ( Figure 7) and represents an adaptive response to accompanied alterations in mitochondrial physiology and dynamics to promote mitochondrial function and support human skin fibroblasts survival.…”

“…*p < .05 denotes a significant difference between groups. kidney epithelial cells, HEK-293 (Kawada et al, 2013). For the same cell line, it was also shown that paxillin mutations induced cell survival advantage and co-localized with the antiapoptotic protein Bcl-2 (Kawada et al, 2013).…”

A Non-genetic Mechanism for Chemoresistance in Lung Cancer: The Role of Integrin β4/Paxillin Axis

“…Further, phosphorylation of PXN activates the ERK pathway, increased Bcl-2 expression, and cisplatin resistance (Wu et al, 2014). Finally, specific PXN mutants, through their interactions with Bcl-2 and dynamin-related protein 1, also regulate cisplatin resistance in human lung cancer cells (Kawada et al, 2013).…”

Inhibiting crosstalk between MET signaling and mitochondrial dynamics and morphology: a novel therapeutic approach for lung cancer and mesothelioma

“…MET is a well-known drug target in NSCLC and also in MPM where it plays a crucial role in disease pathology including cell survival, cell growth, angiogenesis, and metastasis. [1][2][3][4][5] We had previously showed that activation of the MET pathway induced mitochondrial morphology change and affected mitochondrial staining intensity in HEK-293 cells, 36 suggesting that MET may be regulating mitochondrial morphology and functions. In this study, we have provided evidence indicating that indeed, in NSCLC and MPM, MET does regulate mitochondrial structure and function.…”

“…34 We recently showed that mdivi-1 is efficacious in MPM cell lines. 35 Furthermore, we showed that activation of the MET pathway induced changes in mitochondrial morphology and affected mitochondrial staining intensity in HEK-293 cells 36 alluding to possible crosstalk between MET signaling and mitochondrial morphology and functions. Therefore, in this manuscript we explored the effect of combining MET and DRP1 inhibitors on NSCLC and MPM.…”