p21-activated Kinase 1 (Pak1)-dependent Phosphorylation of Raf-1 Regulates Its Mitochondrial Localization, Phosphorylation of BAD, and Bcl-2 Association

Jin, Shenghao; Zhuo, Ya; Guo, Weining; Field, Jeffrey

doi:10.1074/jbc.m413374200

Cited by 138 publications

(117 citation statements)

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“…17,18 Both PAK1 and PAK5 interacted with Raf-1 and phosphorylated it at ser 338, which targeted it to mitochondria. 27,28 These findings imply that PAK5 may play a role in carcinogenesis. So far, PAK5 has not been correlated to any human cancers.…”

Section: Discussionmentioning

confidence: 83%

P21‐activated kinase 5 is overexpressed during colorectal cancer progression and regulates colorectal carcinoma cell adhesion and migration

Gong

Wang

et al. 2009

Intl Journal of Cancer

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P21-activated kinase 5 (PAK5) is the recently identified member of the group B p21-activated kinase (PAK) family which are effectors of the small GTPase Cdc42 and Rac1, known to regulate cell motility and activate cell-survival signaling pathways. However, overexpression of PAK5 has not been associated with any cancers so far. Interestingly, we found that PAK5 was overexpressed in a variety of colorectal carcinoma (CRC) cell lines in a Western-blotting examination. Therefore, in this study, we aim to examine the PAK5 expression during CRC progression and to answer if PAK5 is involved in malignant progression of CRC. By immunohistochemistry, our results showed that PAK5 expression was increased with CRC progression through the adenoma to carcinoma sequence, with the most significant increases in invasive and metastatic CRCs (p < 0.0001). Furthermore, increased PAK5 expression was also found with the development of CRC from lower Duke's grades to higher ones (p < 0.01). Moreover, PAK5 was also increased from well to poorly differentiated CRCs (p < 0.01). Using gain and loss of function experiments, we found that PAK5 reduced CRC cell adhesion but promoted their migration on collagen type I. Taken together, our study demonstrated that PAK5 expression increased significantly with malignant progression of CRC and that PAK5 might promote CRC metastasis by regulating CRC cell adhesion and migration. ' UICCKey words: colorectal carcinoma; PAK5; cancer cell adhesion and migration P21-activated kinases (PAKs), a family of serine/threonine kinases, are small GTPase effectors that play important roles in regulating cell shape, movement, proliferation and survival. [1][2][3] PAKs are characterized by a highly conserved amino-terminal Cdc42/ Rac interactive binding (CRIB) domain and a carboxyl terminal kinase domain. [4][5][6] Six human PAKs were identified and divided into two groups based on their amino acid sequences and their functions. Group A PAKs (PAK1, 2 and 3) share 80 to 90% sequence identity within their catalytic domains, whereas the recently identified group B PAKs (PAK4, 5 and 6), show only approximately 50% identity to the kinase domains of the group A PAKs. 6,7 A marked difference between the two PAK groups is the autologous inhibitory sequence in the NH2-terminal regulatory domain found in group A PAKs, with no obvious homologous sequence in group B. 7 Unlike group A PAKs, whose binding of Cdc42 and Rac leads to their activation, Group B PAKs are not strongly activated by GTPase binding. 8 Of the three group B PAKs, PAK4 was the best characterized, involving in cell adhesion, migration, proliferation and activation of cell-survival pathways that lead to protection from apoptosis. 9,10 Our previous study demonstrated that PAK4 regulated integrin avb5-mediated breast carcinoma cell migration. 11 Different PAK family members have different tissue-specific expression patterns. PAK4 was found to be overexpressed in 78% of a variety of human cancer cell lines, 12 whereas PAK5 and PAK6 showed restricted tissue-spe...

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Section: Discussionmentioning

confidence: 83%

P21‐activated kinase 5 is overexpressed during colorectal cancer progression and regulates colorectal carcinoma cell adhesion and migration

Gong

Wang

et al. 2009

Intl Journal of Cancer

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“…Several recent studies have suggested that the pro-survival effects of Raf-1 can be mediated by phosphorylating Bad on serine 112, which contributes to the inactivation and sequesterization of this pro-apoptotic Bcl-2 family member by 14-3-3 proteins (34,36). Thus, we hypothesized that inhibition of Raf-1 signaling might reduce Bad phosphorylation.…”

Section: Volume 283 • Number 4 • January 25 2008mentioning

confidence: 99%

“…Unless otherwise indicated, doses of specific inhibitors were expected to be maximally effective based on their known IC 50 values. For the Raf-1 inhibitor, we used concentrations within the values reported to block the kinase in intact cells (5-100 M) (36,37).…”

Section: Methodsmentioning

confidence: 99%

Inhibition of Raf-1 Alters Multiple Downstream Pathways to Induce Pancreatic β-Cell Apoptosis

Alejandro¹,

Johnson

2008

Journal of Biological Chemistry

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The serine threonine kinase Raf-1 plays a protective role in many cell types, but its function in pancreatic ␤-cells has not been elucidated. In the present study, we examined whether primary ␤-cells possess Raf-1 and tested the hypothesis that Raf-1 is critical for ␤-cell survival. Using reverse transcriptase-PCR, Western blot, and immunofluorescence, we identified Raf-1 in human islets, mouse islets, and in the MIN6 ␤-cell line. Blocking Raf-1 activity using a specific Raf-1 inhibitor or dominant-negative Raf-1 mutants led to a time-and dose-dependent increase in cell death, assessed by real-time imaging of propidium iodide incorporation, TUNEL, PCR-enhanced DNA laddering, and Caspase-3 cleavage. Although the rapid increase in apoptotic cell death was associated with decreased Erk phosphorylation, studies with two Mek inhibitors suggested that the classical Erkdependent pathway could explain only part of the cell death observed after inhibition of Raf-1. An alternative Erk-independent pathway downstream of Raf-1 kinase involving the pro-apoptotic protein Bad has recently been characterized in other tissues. Inhibiting Raf-1 in ␤-cells led to a striking loss of Bad phosphorylation at serine 112 and an increase in the protein levels of both Bad and Bax. Together, our data strongly suggest that Raf-1 signaling plays an important role regulating ␤-cell survival, via both Erk-dependent and Bad-dependent mechanisms. Conversely, acutely inhibiting phosphatidylinositol 3-kinase Akt had more modest effects on ␤-cell death. These studies identify Raf-1 as a critical anti-apoptotic kinase in pancreatic ␤-cells and contribute to our understanding of survival signaling in this cell type.A reduction in pancreatic ␤-cell survival is a critical pathogenic event in type 1 diabetes, type 2 diabetes, and rare monogenic forms of the disease. Moreover, increased ␤-cell death has been implicated in the failure of clinical islet transplantation (1-3). Several kinases have been investigated for their possible roles in ␤-cell survival, with PI 3 3-kinase and Akt receiving the most attention to date (4 -8). Transgenic mice that overexpress constitutively active Akt in their ␤-cells are protected against streptozotocin-induced diabetes (9, 10) and overexpression of constitutively active Akt protects INS-1 cells from free fatty acid-induced apoptosis (11). However, mice with an 80% reduction in islet Akt activity did not show increased apoptosis or reduced ␤-cell mass (12, 13), suggesting the possibility that other kinases may contribute to ␤-cell survival.The Ras-Raf-mitogen-activated protein kinase cascade mediates pro-survival signals in many cell types. However, this signaling pathway remains understudied in pancreatic ␤-cells. Members of this pathway are found in human and mouse islets, as well as in ␤-cell lines (14 -17). The Raf kinase is a critical hub in this cascade, as it integrates multiple upstream signals and controls several downstream effectors. All three Raf isoforms (A-Raf, B-Raf, and C-Raf/Raf-1) share a common structu...

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“…Interestingly, both CXCL12-CXCR4 and EGF-EGFR lead to activation of the JAK-STAT signaling pathway, which regulates PIM1 expression (Soriano et al, 2003), whereas PMA treatment is also known to produce a rapid induction of PIM1 expression (Wingett et al, 1996). As some of the PIM1 target sites, like the apoptosis regulator BAD (Ser112) or the cell cycle regulator p21 (WAF1) (Thr145/Ser146), are also phosphorylated by other protein kinases, such as RAF1, PAK5, RSK2/5 for the former and PKC- or AKT for the latter (Aho et al, 2004;Jin et al, 2005;Kim et al, 2006, Oh et al, 2006Zhang et al, 2007), it is unlikely that PIM1 is the only kinase that phosphorylates CXCR4-Ser339. Although the exact mechanisms remain to be elucidated, based on our results, PIM1-regulated phosphorylation of CXCR4-S339 could provide an interaction platform for proteins that regulate receptor surface reexon December 15, 2015 jem.rupress.org…”

Section: Methodsmentioning

confidence: 99%

Dissection of PIM serine/threonine kinases in FLT3-ITD–induced leukemogenesis reveals PIM1 as regulator of CXCL12–CXCR4-mediated homing and migration

Grundler¹,

Brault²,

Gasser³

et al. 2009

J Cell Biol

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p21-activated Kinase 1 (Pak1)-dependent Phosphorylation of Raf-1 Regulates Its Mitochondrial Localization, Phosphorylation of BAD, and Bcl-2 Association

Cited by 138 publications

References 44 publications

P21‐activated kinase 5 is overexpressed during colorectal cancer progression and regulates colorectal carcinoma cell adhesion and migration

P21‐activated kinase 5 is overexpressed during colorectal cancer progression and regulates colorectal carcinoma cell adhesion and migration

Inhibition of Raf-1 Alters Multiple Downstream Pathways to Induce Pancreatic β-Cell Apoptosis

Dissection of PIM serine/threonine kinases in FLT3-ITD–induced leukemogenesis reveals PIM1 as regulator of CXCL12–CXCR4-mediated homing and migration

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