P120 catenin regulates dendritic spine and synapse development through Rho-family GTPases and cadherins.
ABSTRACT: Both the cadherin-catenin complex and Rho-family GTPases have been shown to regulate dendrite development. We show here a role for p120 catenin (p120ctn) in regulating spine and synapse formation in the developing mouse brain. p120catenin gene deletion in hippocampal pyramidal neurons in vivo resulted in reduced spine and synapse densities along dendrites. In addition, p120 catenin loss resulted in reduced cadherin levels and misregulation of Rho-family GTPases, with decreased Rac1 and increased RhoA activity. Analyses in vitro indicate that the reduced spine density reflects aberrant Rho-family GTPase signaling, whereas the effects on spine maturation appear to result from reduced cadherin levels and possibly aberrant Rho-family GTPase signaling. Thus, p120ctn acts as a signal coordinator between cadherins and Rho-family GTPases to regulate cytoskeletal changes required during spine and synapse development.
Project description:Schwann cell myelin contains highly compacted layers of membrane as well as noncompacted regions with a visible cytoplasm. One of these cytoplasmic compartments is the Schmidt-Lanterman incisure, which spirals through the compacted layers and is believed to help sustain the growth and function of compact myelin. Incisures contain adherens junctions (AJs), the key components of which are E-cadherin, its cytoplasmic partners called catenins, and F-actin. To explore in vivo the role of cadherin and catenins in incisures, E-cadherin mutant proteins that completely replace endogenous cadherin have been delivered to the cells using adenovirus. When the introduced cadherin lacked its extracellular domain, association of p120 catenin (p120ctn) with the cadherin did not occur, and incisures disappeared. Remarkably, the additional replacement of two phosphorylatable tyrosines by phenylalanine in the cytoplasmic tail of the mutant cadherin restored both p120ctn binding and incisure architecture, indicating that p120ctn recruitment is critical for incisures maintenance and might be regulated by phosphorylations. In addition, the ability of the p120ctn/cadherin complex to support incisures was blocked by mutation of the Rho GTPase regulatory region of the p120ctn, and downregulation of Rac1 activity at the junction reversed this inhibition. Because Rho GTPases regulate the state of the actin filaments, these findings suggest that one role of p120ctn in incisures is to organize the cytoskeleton at the AJ. Finally, developmental studies of Schwann cells demonstrated that p120ctn recruitment from the cytoplasm to the AJ occurs before the appearance of Rac1 GTPase and F-actin at the junction.
Project description:The adherens junction protein p120-catenin (p120ctn) shuttles between E-cadherin-bound and cytoplasmic pools to regulate E-cadherin/catenin complex stability and cell migration, respectively. When released from the adherens junction, p120ctn promotes cell migration through modulation of the Rho GTPases Rac1, Cdc42, and RhoA. Accordingly, the down-regulation and cytoplasmic mislocalization of p120ctn has been reported in all subtypes of lung cancers and is associated with grave prognosis. Previously, we reported that cigarette smoke induced cytoplasmic translocation of p120ctn and cell migration, but the underlying mechanism was unclear. Using primary human bronchial epithelial cells exposed to smoke-concentrated medium (Smk), we observed the translocation of Rac1 and Cdc42, but not RhoA, to the leading edge of polarized and migrating human bronchial epithelial cells. Rac1 and Cdc42 were robustly activated by smoke, whereas RhoA was inhibited. Accordingly, siRNA knockdown of Rac1 or Cdc42 completely abolished Smk-induced cell migration, whereas knockdown of RhoA had no effect. p120ctn/Rac1 double knockdown completely abolished Smk-induced cell migration, whereas p120ctn/Cdc42 double knockdown did not. These data suggested that Rac1 and Cdc42 coactivation was essential to smoke-promoted cell migration in the presence of p120ctn, whereas migration proceeded via Rac1 alone in the absence of p120ctn. Thus, Rac1 may provide an omnipotent therapeutic target in reversing cell migration during the early (intact p120ctn) and late (loss of p120ctn) stages of lung carcinogenesis.
Project description:Cyclin-dependent kinase 5 (CDK5) plays important roles in synaptic function. Its unregulated over-activation has been, however, associated with neurodegeneration in Alzheimer's disease. Our previous studies revealed that CDK5 silencing ameliorates tauopathy and spatial memory impairment in the 3xTgAD mouse model. However, how CDK5 targeting affects synaptic adhesion proteins, such as those involved in the cadherin/catenin system, during learning and memory processes is not completely understood. In this study, we detected reduced expression of p120 catenin (p120 ctn), N-cadherin, and ?-catenin in the brain of human Alzheimer's disease patients, in addition to a reduced PSD95 and GluN2B protein levels in a 3xTgAD mouse model. Such decrease in synaptic proteins was recovered by CDK5 silencing in mice leading to a better learning and memory performance. Additionally, CDK5 inhibition or knockout increased p120 ctn levels. Moreover, in a glutamate-induced excitotoxicity model, CDK5 silencing-induced neuroprotection depended on p120 ctn. Together, those findings suggest that p120 ctn plays an important role in the neuronal dysfunction of Alzheimer's disease models and contributes to CDK5 silencing-induced neuroprotection and improvement of memory function. p120ctn is part of the synaptic adhesion molecular complex N-cadh/p120ctn/B-ctn/PSD95, and it has a pivotal role in cell adhesion stabilization and dendritic spine modulation. Our data show that synaptic adhesion complex is affected in AD human brains and in AD models. This complex is recovered by the silencing of CDK5, preventing memory dysfunction in an AD mice model and contributing to the neuroprotection in a depend-mode of p120ctn.
Project description:Localization of presynaptic components to synaptic sites is critical for hippocampal synapse formation. Cell adhesion-regulated signaling is important for synaptic development and function, but little is known about differentiation of the presynaptic compartment. In this study, we describe a pathway that promotes presynaptic development involving p120catenin (p120ctn), the cytoplasmic tyrosine kinase Fer, the protein phosphatase SHP-2, and beta-catenin. Presynaptic Fer depletion prevents localization of active zone constituents and synaptic vesicles and inhibits excitatory synapse formation and synaptic transmission. Depletion of p120ctn or SHP-2 similarly disrupts synaptic vesicle localization with active SHP-2, restoring synapse formation in the absence of Fer. Fer or SHP-2 depletion results in elevated tyrosine phosphorylation of beta-catenin. beta-Catenin overexpression restores normal synaptic vesicle localization in the absence of Fer or SHP-2. Our results indicate that a presynaptic signaling pathway through p120ctn, Fer, SHP-2, and beta-catenin promotes excitatory synapse development and function.
Project description:The catenin p120 (p120ctn) is an armadillo repeat domain protein that binds to cadherins and has been shown to facilitate strong cell-cell adhesion. We have investigated a possible link between heterotrimeric G proteins and p120ctn, and found that both Galpha12 and Galpha13 can completely and selectively abrogate the p120ctn-induced branching phenotype in different cell types. Consistent with these observations, the expression of Galpha12 or Galpha13 compensates for the reduction of Rho activity induced by p120ctn. On the other hand, p120ctn can be selectively coimmunoprecipitated with Galpha12, and the coimmunoprecipitation was favored by activation of the G protein. A specific interaction between p120ctn and Galpha12Q231L was also observed in in vitro binding experiments. In addition, p120ctn can be immunoprecipitated along with Galpha12Q231L in L cells in absence of E-cadherin. Interestingly, the expression of Galpha12Q231L increases the amount of p120ctn associated with E-cadherin. These findings demonstrate that Galpha12 and p120ctn are binding partners, and they also suggest a role for Galpha12 in regulating p120ctn activity and its interaction with cadherins. We propose that the Galpha12-p120ctn interaction acts as a molecular switch, which regulates cadherin-mediated cell-cell adhesion.
Project description:E-cadherin-mediated cell-cell adhesion is critical for naive pluripotency of cultured mouse embryonic stem cells (mESCs). E-cadherin-depleted mESC fail to downregulate their pluripotency program and are unable to initiate lineage commitment. To further explore the roles of cell adhesion molecules during mESC differentiation, we focused on p120 catenin (p120ctn). Although one key function of p120ctn is to stabilize and regulate cadherin-mediated cell-cell adhesion, it has many additional functions, including regulation of transcription and Rho GTPase activity. Here, we investigated the role of mouse p120ctn in early embryogenesis, mESC pluripotency and early fate determination. In contrast to the E-cadherin-null phenotype, p120ctn-null mESCs remained pluripotent, but their in vitro differentiation was incomplete. In particular, they failed to form cystic embryoid bodies and showed defects in primitive endoderm formation. To pinpoint the underlying mechanism, we undertook a structure-function approach. Rescue of p120ctn-null mESCs with different p120ctn wild-type and mutant expression constructs revealed that the long N-terminal domain of p120ctn and its regulatory domain for RhoA were dispensable, whereas its armadillo domain and interaction with E-cadherin were crucial for primitive endoderm formation. We conclude that p120ctn is not only an adaptor and regulator of E-cadherin, but is also indispensable for proper lineage commitment.
Project description:The cadherin-catenin complex is essential for tissue morphogenesis during animal development. In cultured mammalian cells, p120 catenin (p120ctn) is an important regulator of cadherin-catenin complex function. However, information on the role of p120ctn family members in cadherin-dependent events in vivo is limited. We have examined the role of the single Caenorhabditis elegans p120ctn homologue JAC-1 (juxtamembrane domain [JMD]-associated catenin) during epidermal morphogenesis. Similar to other p120ctn family members, JAC-1 binds the JMD of the classical cadherin HMR-1, and GFP-tagged JAC-1 localizes to adherens junctions in an HMR-1-dependent manner. Surprisingly, depleting JAC-1 expression using RNA interference (RNAi) does not result in any obvious defects in embryonic or postembryonic development. However, jac-1(RNAi) does increase the severity and penetrance of morphogenetic defects caused by a hypomorphic mutation in the hmp-1/alpha-catenin gene. In these hmp-1 mutants, jac-1 depletion causes failure of the embryo to elongate into a worm-like shape, a process that involves contraction of the epidermis. Associated with failed elongation is the detachment of actin bundles from epidermal adherens junctions and failure to maintain cadherin in adherens junctions. These results suggest that JAC-1 acts as a positive modulator of cadherin function in C. elegans.
Project description:Vascular endothelial cadherin (VE-cadherin) mediates homophylic adhesion between endothelial cells and is an important regulator of angiogenesis, blood vessel permeability and leukocyte trafficking. Rac1, a member of the Rho family of GTPases, controls VE-cadherin adhesion by acting downstream of several growth factors, including angiopoietin-1 and vascular endothelial growth factor (VEGF). Here we show that UTP-induced activation of the Gq protein-coupled P2Y2 nucleotide receptor (P2Y2R) in human coronary artery endothelial cells (HCAECs) activated Rac1 and caused a transient complex to form between P2Y2R, VE-cadherin and VEGF receptor-2 (VEGFR-2). Knockdown of VE-cadherin expression with siRNA did not affect UTP-induced activation of extracellular signal-regulated kinases 1/2 (ERK1/2) but led to a loss of UTP-induced Rac1 activation and tyrosine phosphorylation of p120 catenin, a cytoplasmic protein known to interact with VE-cadherin. Activation of the P2Y2R by UTP also caused a prolonged interaction between p120 catenin and vav2 (a guanine nucleotide exchange factor for Rac) that correlated with the kinetics of UTP-induced tyrosine phosphorylation of p120 catenin and VE-cadherin. Inhibitors of VEGFR-2 (SU1498) or Src (PP2) significantly diminished UTP-induced Rac1 activation, tyrosine phosphorylation of p120 catenin and VE-cadherin, and association of the P2Y2R with VE-cadherin and p120 catenin with vav2. These findings suggest that the P2Y2R uses Src and VEGFR-2 to mediate association of the P2Y2R with VE-cadherin complexes in endothelial adherens junctions to activate Rac1.
Project description:BACKGROUND:Epithelial ovarian cancer (EOC) remains one of the most lethal gynecologic cancers, and its pathogenetic mechanism remains unclear. Here we show that MUC16 promotes the translocation of p120-catenin (p120ctn) to the cytoplasm and consequently activates ras homolog (Rho) GTPases RhoA/Cdc42 activation to modulate the proliferation and migration abilities of EOC cells. METHODS:We collect 94 ovarian cancer (OC) patients' tissue samples to constitute tissue microarray (TMA) and analyze the MUC16 and p120ctn expression levels. Lentivirus transfection is used to overexpress cytoplasmic tail domain (CTD) of MUC16 and CRISPR/Cas9 genome-editing system is firstly used to knock out MUC16 in EOC cells. The proliferation or migration ability of cells is analyzed by MTS or migration assay. RESULTS:We find that MUC16 and p120ctn are aberrantly overexpressed in 94 clinical OC samples compared with benign ovarian tumors (BOT). MUC16 is a critical inducer of the proliferation and migration of EOC cells and the CTD of MUC16 plays an important role during this process. In addition, we reveal the relationship between MUC16 and p120ctn, which has not previously been studied. We show that MUC16 promotes the translocation of p120ctn to the cytoplasm and consequently activates Rho GTPases to modulate the proliferation and migration abilities of EOC cells. The cell proliferation and migration abilities induced by MUC16 are mediated by p120ctn through RhoA/Cdc42 activation. CONCLUSIONS:The highly expressed MUC16 promotes the translocation of p120ctn to the cytoplasm, where it activates RhoA/Cdc42 to modulate the proliferation and migration abilities of EOC cells. These findings may provide new targets for the treatment of EOC.
Project description:The gamma-secretase complex cleaves many transmembrane proteins, including amyloid precursor protein, EphB and ErbB tyrosine kinase receptors, Notch1 receptors, and adhesion factors. Presenilin 1, the catalytic subunit of gamma-secretase, associates with the cadherin/catenin cell-cell adhesion/communication system and promotes cadherin processing (Georgakopoulos, A., et al. (1999) Mol. Cell 4, 893-902; Marambaud, P., et al. (2002) EMBO J. 21, 1948-1956), but the mechanism by which gamma-secretase and cadherins associate is unclear. Here we report that p120 catenin (p120ctn), a component of the cadherin-catenin complex, recruits gamma-secretase to cadherins, thus stimulating their processing while inhibiting production of Abeta peptide and the amyloid precursor protein intracellular domain. This function of p120ctn depends on both p120ctn-cadherin and p120ctn-presenilin 1 binding, indicating that p120ctn is the central factor that bridges gamma-secretase and cadherin-catenin complexes. Our data show that p120ctn is a unique positive regulator of the gamma-secretase processing of cadherins and a negative regulator of the amyloid precursor protein processing. Furthermore, our data suggest that specific members of the gamma-secretase complex may be used to recruit different substrates and that distinct PS1 sequences are required for processing of APP and cadherins.