JNK1 and JNK2 Oppositely Regulate p53 in Signaling Linked to Apoptosis Triggered by an Altered Fibronectin Matrix

Abstract

The extracellular matrix regulates many cellular processes, including survival, and alterations in the matrix or in matrix survival signals can trigger apoptosis. Previously, we showed that an altered fibronectin matrix triggers apoptosis in primary cells via a novel pathway regulated by transcriptionally mediated decreases in p53 and c-Myc levels. Here we report that this apoptotic mechanism is propagated by decreased phosphorylation of focal adhesion kinase (FAK), which is linked to increased phosphorylation of c-Jun N-terminal kinase (JNK) and to decreased levels of p53. FAK is physically and spatially linked to JNK and p53, which relocalize from the nucleus to the cell membrane to mediate this interaction. Further, p53 participates in a feedback mechanism with JNK to regulate this apoptotic process and is oppositely regulated by JNK1 and JNK2.Alterations in the extracellular matrix during inflammation, development, or metastatic processes can alter the cellular biology that governs these processes. Under these conditions, an altered matrix can result from proteolytic cleavage or alternative splicing of matrix molecules. In inflammation, proteolysis of extracellular matrix molecules leads to the formation of fragments, such as fibronectin (FN) 1 fragments, that elicit cellular responses different from those elicited by the intact molecule (1-5). For example, disease-associated fragments of FN trigger p53-mediated apoptosis of primary cells, but the intact molecule does not (6 -8). Similarly, alternatively spliced variants of FN elicit different cell responses, and specific domains of FN regulate cell survival (4, 5).Previously we reported that an altered FN matrix triggers apoptosis in primary cells via a novel pathway that is regulated by transcriptionally mediated decreases in p53 and c-Myc levels in primary cells (5). To further decipher this apoptotic pathway, we explored the possible connections between integrin/FAK-mediated signals and the down-regulation of p53. We hypothesized that c-Jun N-terminal kinase (JNK) might be at the crossroads of this signaling pathway, since FAK and associated focal adhesion proteins (Rac1/Pak1/MKK4/JNK) have been linked to p53 status in the apoptosis of primary cells (9, 10). In addition, JNK can phosphorylate (11) and form a complex with p53 to stabilize it (12-16), thereby influencing its activity directly.FAK is an integrin-associated protein tyrosine kinase that is important in integrin signaling. Its activation, triggered by increased phosphorylation of Tyr 397 and other sites, has been implicated in many cellular processes, including cell survival. The N-terminal domain of FAK directs interactions with integrins and growth factor receptors. FAK also has a central catalytic domain, which contains Tyr 397 , a major autophosphorylation site and a site of interaction with the Src homology 2 domain. Its C-terminal noncatalytic domain, also known as FAK-related non-kinase (FRNK), contains sites for multiple protein-protein interactions and a focal adhesion targeting (FA...

NG2, a novel proapoptotic receptor, opposes integrin α4 to mediate anoikis through PKCα-dependent suppression of FAK phosphorylation

“…As previously shown, [1][2][3] an altered FN matrix consisting of the V þ HÀ protein induced apoptosis in primary ligament fibroblasts (Figure 1a and b). Cells treated with an altered FN matrix exhibited nuclear condensation and bright DAPI staining typical of apoptotic cells.…”

NG2, a novel proapoptotic receptor, opposes integrin α4 to mediate anoikis through PKCα-dependent suppression of FAK phosphorylation

“…As previously shown, [1][2][3] an altered FN matrix consisting of the V þ HÀ protein induced apoptosis in primary ligament fibroblasts (Figure 1a and b). Cells treated with an altered FN matrix exhibited nuclear condensation and bright DAPI staining typical of apoptotic cells.…”

Linking JNK Activity to the DNA Damage Response

“…However, JNK1 and JNK2 are known to mediate opposite effects on p53, with JNK1 proposed to negatively regulate p53, while JNK2 acts as a positive regulator of p53. 103 Overall, the results presented here illustrate the complex interactions involving JNKs in the regulation of the cellular response to DNA damage (Figure 1). In particular, no future studies should exclude assessment of the individual proteins arising from the expression of the 3 jnk genes.…”

c‑Jun N‑terminal kinase inhibition attenuates early brain injury induced neuronal apoptosis via decreasing p53 phosphorylation and mitochondrial apoptotic pathway activation in subarachnoid hemorrhage rats

“…It was suggested that JNK1 functions as a negative regulator in the process (13). Furthermore, an additional study investigating signaling in a model of fibronectin fragment-mediated apoptosis verified this conclusion (29). However, in the present study, the opposite phenomenon was observed, suggesting that JNK1 may interact with p53 differently according to the prevailing circumstances.…”

NG2, a novel proapoptotic receptor, opposes integrin α4 to mediate anoikis through PKCα-dependent suppression of FAK phosphorylation

“…As previously shown, [1][2][3] an altered FN matrix consisting of the V þ HÀ protein induced apoptosis in primary ligament fibroblasts (Figure 1a and b). Cells treated with an altered FN matrix exhibited nuclear condensation and bright DAPI staining typical of apoptotic cells.…”

Linking JNK Activity to the DNA Damage Response

“…However, JNK1 and JNK2 are known to mediate opposite effects on p53, with JNK1 proposed to negatively regulate p53, while JNK2 acts as a positive regulator of p53. 103 Overall, the results presented here illustrate the complex interactions involving JNKs in the regulation of the cellular response to DNA damage (Figure 1). In particular, no future studies should exclude assessment of the individual proteins arising from the expression of the 3 jnk genes.…”

c‑Jun N‑terminal kinase inhibition attenuates early brain injury induced neuronal apoptosis via decreasing p53 phosphorylation and mitochondrial apoptotic pathway activation in subarachnoid hemorrhage rats

“…It was suggested that JNK1 functions as a negative regulator in the process (13). Furthermore, an additional study investigating signaling in a model of fibronectin fragment-mediated apoptosis verified this conclusion (29). However, in the present study, the opposite phenomenon was observed, suggesting that JNK1 may interact with p53 differently according to the prevailing circumstances.…”

NG2, a novel proapoptotic receptor, opposes integrin α4 to mediate anoikis through PKCα-dependent suppression of FAK phosphorylation

“…As previously shown, [1][2][3] an altered FN matrix consisting of the V þ HÀ protein induced apoptosis in primary ligament fibroblasts (Figure 1a and b). Cells treated with an altered FN matrix exhibited nuclear condensation and bright DAPI staining typical of apoptotic cells.…”

Linking JNK Activity to the DNA Damage Response

“…However, JNK1 and JNK2 are known to mediate opposite effects on p53, with JNK1 proposed to negatively regulate p53, while JNK2 acts as a positive regulator of p53. 103 Overall, the results presented here illustrate the complex interactions involving JNKs in the regulation of the cellular response to DNA damage (Figure 1). In particular, no future studies should exclude assessment of the individual proteins arising from the expression of the 3 jnk genes.…”

c‑Jun N‑terminal kinase inhibition attenuates early brain injury induced neuronal apoptosis via decreasing p53 phosphorylation and mitochondrial apoptotic pathway activation in subarachnoid hemorrhage rats

“…It was suggested that JNK1 functions as a negative regulator in the process (13). Furthermore, an additional study investigating signaling in a model of fibronectin fragment-mediated apoptosis verified this conclusion (29). However, in the present study, the opposite phenomenon was observed, suggesting that JNK1 may interact with p53 differently according to the prevailing circumstances.…”