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Rac1-PAK1 regulation of Rab11 cycling promotes junction destabilization.

ABSTRACT: Rac1 GTPase is hyperactivated in tumors and contributes to malignancy. Rac1 disruption of junctions requires its effector PAK1, but the precise mechanisms are unknown. Here, we show that E-cadherin is internalized via micropinocytosis in a PAK1-dependent manner without catenin dissociation and degradation. In addition to internalization, PAK1 regulates E-cadherin transport by fine-tuning Rab small GTPase function. PAK1 phosphorylates a core Rab regulator, RabGDIβ, but not RabGDIα. Phosphorylated RabGDIβ preferentially associates with Rab5 and Rab11, which is predicted to promote Rab retrieval from membranes. Consistent with this hypothesis, Rab11 is activated by Rac1, and inhibition of Rab11 function partially rescues E-cadherin destabilization. Thus, Rac1 activation reduces surface cadherin levels as a net result of higher bulk flow of membrane uptake that counteracts Rab11-dependent E-cadherin delivery to junctions (recycling and/or exocytosis). This unique small GTPase crosstalk has an impact on Rac1 and PAK1 regulation of membrane remodeling during epithelial dedifferentiation, adhesion, and motility.

SUBMITTER: Erasmus JC

PROVIDER: S-EPMC8091128 | biostudies-literature |

REPOSITORIES: biostudies-literature

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EIF4A3-induced circBRWD3 promotes tumorigenesis of breast cancer through miR-142-3p_miR-142-5p/RAC1/PAK1 signaling

Project description:CircBRWD3 is a newly discovered circRNA, and its potential function has not been probed. Here, we aimed to molecularly dissect the role of circBRWD3 in the tumorigenesis and progression of breast cancer (BC). qRT-PCR analysis revealed that circBRWD3 expression was dramatically upregulated in BC tissues, a feature that was positively correlated with the poor prognosis of patients with BC. CircBRWD3 knockdown repressed cell proliferation and metastasis, while promoting cell apoptosis in vitro. Consistently, an in vivo circBRWD3 deficiency model exhibited suppressed tumor metastasis and oncogenesis. On the other hand, circBRWD3 overexpression promoted cancer cell activity and tumorigenesis. Further, mechanistic studies elucidated that circBRWD3 sponged both miR-142-3p and miR-142-5p to modulate RAC1 expression, which subsequently activated the RAC1/PAK1 signaling to facilitate the tumorigenesis and progression of BC. Moreover, we discovered that EIF4A3 facilitated circBRWD3 expression by targeting the upstream of BRWD3 pre-mRNA. In conclusion, our study reveals that circBRWD3 facilitates BC tumorigenesis by regulating the circBRWD3/miR-142-3p_miR-142-5p /RAC1/PAK1 axis. In addition, circBRWD3 expression is positively regulated by an RNA-binding protein, EIFA3. Our results provide valuable scientific data for early diagnosis and therapy for breast cancer patients. Supplementary Information The online version contains supplementary material available at 10.1186/s12885-022-10200-7.

| S-EPMC9703775 | biostudies-literature

A Trio-Rac1-Pak1 signalling axis drives invadopodia disassembly.

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| S-EPMC4083618 | biostudies-literature

Mtss1 promotes cell-cell junction assembly and stability through the small GTPase Rac1.

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The metastatic promoter DEPDC1B induces epithelial-mesenchymal transition and promotes prostate cancer cell proliferation via Rac1-PAK1 signaling.

Project description:Metastasis is the major cause of prostate cancer (PCa)-related mortality. Epithelial-mesenchymal transition (EMT) is a vital characteristic feature that empowers cancer cells to adapt and survive at the beginning of metastasis. Therefore, it is essential to identify the regulatory mechanism of EMT in metastatic prostate cancer (mPCa) and to develop a novel therapy to block PCa metastasis. Here, we discovered a novel PCa metastasis oncogene, DEP domain containing 1B (DEPDC1B), which was positively correlated with the metastasis status, high Gleason score, advanced tumor stage, and poor prognosis. Functional assays revealed that DEPDC1B enhanced the migration, invasion, and proliferation of PCa cells in vitro and promoted tumor metastasis and growth in vivo. Mechanistic investigations clarified that DEPDC1B induced EMT and enhanced proliferation by binding to Rac1 and enhancing the Rac1-PAK1 pathway. This DEPDC1B-mediated oncogenic effect was reversed by a Rac1-GTP inhibitor or Rac1 knockdown. In conclusion, we discover that the DEPDC1B-Rac1-PAK1 signaling pathway may serve as a multipotent target for clinical intervention in mPCa.

| S-EPMC7536616 | biostudies-literature

Rac1/Pak1/p38/MMP-2 Axis Regulates Angiogenesis in Ovarian Cancer.

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| S-EPMC4417466 | biostudies-literature

CYK4 inhibits Rac1-dependent PAK1 and ARHGEF7 effector pathways during cytokinesis.

Project description:In mitosis, animal cells lose their adhesion to the surrounding surfaces and become rounded. During mitotic exit, they reestablish these adhesions and at the same time physically contract and divide. How these competing processes are spatially segregated at the cell cortex remains mysterious. To address this question, we define the specific effector pathways used by RhoA and Rac1 in mitotic cells. We demonstrate that the MKlp1-CYK4 centralspindlin complex is a guanosine triphosphatase-activating protein (GAP) for Rac1 and not RhoA and that CYK4 negatively regulated Rac1 activity at the cell equator in anaphase. Cells expressing a CYK4 GAP mutant had defects in cytokinesis and showed elevated staining for the cell adhesion marker vinculin. These defects could be rescued by depletion of ARHGEF7 and p21-activated kinase, Rac1-specific effector proteins required for cell adhesion. Based on these findings, we propose that CYK4 GAP activity is required during anaphase to inhibit Rac1-dependent effector pathways associated with control of cell spreading and adhesion.

| S-EPMC3432774 | biostudies-literature

RIT1 controls actin dynamics via complex formation with RAC1/CDC42 and PAK1.

Project description:RIT1 belongs to the RAS family of small GTPases. Germline and somatic RIT1 mutations have been identified in Noonan syndrome (NS) and cancer, respectively. By using heterologous expression systems and purified recombinant proteins, we identified the p21-activated kinase 1 (PAK1) as novel direct effector of RIT1. We found RIT1 also to directly interact with the RHO GTPases CDC42 and RAC1, both of which are crucial regulators of actin dynamics upstream of PAK1. These interactions are independent of the guanine nucleotide bound to RIT1. Disease-causing RIT1 mutations enhance protein-protein interaction between RIT1 and PAK1, CDC42 or RAC1 and uncouple complex formation from serum and growth factors. We show that the RIT1-PAK1 complex regulates cytoskeletal rearrangements as expression of wild-type RIT1 and its mutant forms resulted in dissolution of stress fibers and reduction of mature paxillin-containing focal adhesions in COS7 cells. This effect was prevented by co-expression of RIT1 with dominant-negative CDC42 or RAC1 and kinase-dead PAK1. By using a transwell migration assay, we show that RIT1 wildtype and the disease-associated variants enhance cell motility. Our work demonstrates a new function for RIT1 in controlling actin dynamics via acting in a signaling module containing PAK1 and RAC1/CDC42, and highlights defects in cell adhesion and migration as possible disease mechanism underlying NS.

| S-EPMC5937737 | biostudies-literature

DEP Domain-Containing Protein 1B (DEPDC1B) Promotes Migration and Invasion in Pancreatic Cancer Through the Rac1/PAK1-LIMK1-Cofilin1 Signaling Pathway.

Project description:Background:With increasing incidence, pancreatic cancer (PC) is one of the most common digestive tract tumors. However, the prognosis of PC is particularly dismal due to the highly invasive and metastatic behavior of this deadly disease. DEP domain-containing protein 1B (DEPDC1B), which is overexpressed in multiple tumors, such as breast cancer, oral cancer and non-small cell lung cancer, plays a significant role in cell movement, cell cycle and cytoskeleton reorganization. However, the function of DEPDC1B in PC remains poorly understood. Methods:The function of DEPDC1B in the migration and invasion of PC was evaluated by wound healing and Transwell assays in vitro and PC-derived liver metastasis models in vivo. The molecular mechanisms of DEPDC1B were investigated through cell line establishment, Western blotting, qRT-PCR, immunoprecipitation, histological examination and immunohistochemistry analysis. Results:DEPDC1B was overexpressed in PC cell lines. DEPDC1B regulated cell migration and invasion. DEPDC1B regulated the Rac1/PAK1-LIMK1-cofilin1 signaling pathway by interacting with Rac1. Rac1 inhibition suppressed DEPDC1B-induced migration and invasion in PC in vitro and DEPDC1B-induced liver metastasis in vivo. Conclusion:DEPDC1B promoted cell migration and invasion by activating the Rac1/PAK1-LIMK1-cofilin1 signaling pathway, thus providing a potential therapeutic target against PC.

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Interaction of phosphorylated Rab11-FIP2 with Eps15 regulates apical junction composition.

Project description:MARK2 regulates the establishment of polarity in Madin-Darby canine kidney (MDCK) cells in part through phosphorylation of serine 227 of Rab11-FIP2. We identified Eps15 as an interacting partner of phospho-S227-Rab11-FIP2 (pS227-FIP2). During recovery from low calcium, Eps15 localized to the lateral membrane before pS227-FIP2 arrival. Later in recovery, Eps15 and pS227-FIP2 colocalized at the lateral membrane. In MDCK cells expressing the pseudophosphorylated FIP2 mutant FIP2(S227E), during recovery from low calcium, Eps15 was trapped and never localized to the lateral membrane. Mutation of any of the three NPF domains within GFP-FIP2(S227E) rescued Eps15 localization at the lateral membrane and reestablished single-lumen cyst formation in GFP-FIP2(S227E)-expressing cells in three-dimensional (3D) culture. Whereas expression of GFP-FIP2(S227E) induced the loss of E-cadherin and occludin, mutation of any of the NPF domains of GFP-FIP2(S227E) reestablished both proteins at the apical junctions. Knockdown of Eps15 altered the spatial and temporal localization of pS227-FIP2 and also elicited formation of multiple lumens in MDCK 3D cysts. Thus an interaction of Eps15 and pS227-FIP2 at the appropriate time and location in polarizing cells is necessary for proper establishment of epithelial polarity.

| S-EPMC5391185 | biostudies-literature

Liposome reconstitution and modulation of recombinant prenylated human Rac1 by GEFs, GDI1 and Pak1.

Project description:Small Rho GTPases are well known to regulate a variety of cellular processes by acting as molecular switches. The regulatory function of Rho GTPases is critically dependent on their posttranslational modification at the carboxyl terminus by isoprenylation and association with proper cellular membranes. Despite numerous studies, the mechanisms of recycling and functional integration of Rho GTPases at the biological membranes are largely unclear. In this study, prenylated human Rac1, a prominent member of the Rho family, was purified in large amount from baculovirus-infected Spodoptera frugiperda insect cells using a systematic detergent screening. In contrast to non-prenylated human Rac1 purified from Escherichia coli, prenylated Rac1 from insect cells was able to associate with synthetic liposomes and to bind Rho-specific guanine nucleotide dissociation inhibitor 1 (GDI1). Subsequent liposome reconstitution experiments revealed that GDI1 efficiently extracts Rac1 from liposomes preferentially in the inactive GDP-bound state. The extraction was prevented when Rac1 was activated to its GTP-bound state by Rac-specific guanine nucleotide exchange factors (GEFs), such as Vav2, Dbl, Tiam1, P-Rex1 and TrioN, and bound by the downstream effector Pak1. We found that dissociation of Rac1-GDP from its complex with GDI1 strongly correlated with two distinct activities of especially Dbl and Tiam1, including liposome association and the GDP/GTP exchange. Taken together, our results provided first detailed insights into the advantages of the in vitro liposome-based reconstitution system to study both the integration of the signal transducing protein complexes and the mechanisms of regulation and signaling of small GTPases at biological membranes.

| S-EPMC4094549 | biostudies-literature

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