Association Of Cortactin Research Articles

Association of Cortactin and MDM2 in Solid Ameloblastoma and its Malignant Counterpart

Ameloblastoma is characterized by heterogeneity regarding its pathogenetic development, molecular abnormalities, and clinical course. Determining the molecular basis underlying these important differences remains challenging. Nevertheless, identifying molecules that influence tumor behavior would be the first steps towards gaining some insights into its pathobiology. MDM2, a 90-95kDa protein coded by a mdm2 gene which is mapped on chromosome 12q13-14. MDM2 is a negative regulator of p53 activity, through binding to the transcriptional activation domain of p53 leading to proteasome-mediated degradation, Cortactin, a product of CTTN gene, mapped to human chromosome 11q13 regulates actin-related (Arp2/3) complex induction of actin polymerization during invadopodia formation, thereby promoting cell motility. This has been accomplished through its involvement in all steps of the invadosome lifecycle, from the assembly, maturation, proteolytic activity, and disassembly. This study aims to evaluate the association of both MDM2 and Cortactin expression in solid ameloblastoma and its malignant counterpart and analyzing their significance. 10 cases of SAB with its different histologic variants and 20 cases malignant variants of ameloblastoma tumors were collected. An immunohistochemical investigation using, Cortactin, and MDM2 antibodies were done for all specimens. There was a statistically significant difference between malignant group and benign group. According to the current study Cortactin and MDM2 can be useful when considering the diagnosis of malignancy.

The Association of Cortactin with Profilin-1 Is Critical for Smooth Muscle Contraction

Profilin-1 (Pfn-1) is an actin-regulatory protein that has a role in modulating smooth muscle contraction. However, the mechanisms that regulate Pfn-1 in smooth muscle are not fully understood. Here, stimulation with acetylcholine induced an increase in the association of the adapter protein cortactin with Pfn-1 in smooth muscle cells/tissues. Furthermore, disruption of the protein/protein interaction by a cell-permeable peptide (CTTN-I peptide) attenuated actin polymerization and smooth muscle contraction without affecting myosin light chain phosphorylation at Ser-19. Knockdown of cortactin by lentivirus-mediated RNAi also diminished actin polymerization and smooth muscle force development. However, cortactin knockdown did not affect myosin activation. In addition, cortactin phosphorylation has been implicated in nonmuscle cell migration. In this study, acetylcholine stimulation induced cortactin phosphorylation at Tyr-421 in smooth muscle cells. Phenylalanine substitution at this position impaired cortactin/Pfn-1 interaction in response to contractile activation. c-Abl is a tyrosine kinase that is necessary for actin dynamics and contraction in smooth muscle. Here, c-Abl silencing inhibited the agonist-induced cortactin phosphorylation and the association of cortactin with Pfn-1. Finally, treatment with CTTN-I peptide reduced airway resistance and smooth muscle hyperreactivity in a murine model of asthma. These results suggest that the interaction of cortactin with Pfn-1 plays a pivotal role in regulating actin dynamics, smooth muscle contraction, and airway hyperresponsiveness in asthma. The association of cortactin with Pfn-1 is regulated by c-Abl-mediated cortactin phosphorylation.

Myosin IIB deficiency in embryonic fibroblasts affects regulators and core members of the par polarity complex

Wild-type (WT) and myosin heavy chain IIB null [MHCIIB (-/-)] embryonic fibroblasts were used as an experimental model to assess the role of the isoform B of myosin II (MII) in the regulation of the cell shape and intrinsic polarity. Genetic ablation of MHCIIB causes a persistent albeit, unstable protrusive activity in embryonic fibroblasts (Lo et al. in Nonmuscle myosin IIB is involved in the guidance of fibroblast migration. Mol Biol Cell 15:982-989, 2004). Here, we show that MHCIIB-deficient fibroblasts are characterized by a sustained guanine nucleotide exchange factor (GEF)-dependent activation of the small GTPase Rac-1 that is responsible for the continual lamellipodium formation. Moreover, we observed a sustained PKC-ζ activation and an increased association of cortactin with the plasma membrane in the MHCIIB (-/-) cells that were also dependent on GEF-mediated Rac-1 activation. Rac-1 activation and its downstream effects were induced in WT fibroblasts by inhibiting MII ATPase and crosslinking activities, suggesting that an altered actin-MII interaction favours Rac-1 activation, regardless of the MII isoform implicated. In addition, we found MIIB isoform-specific effects that were independent of Rac-1 activation. MHCIIA interacts with cortactin whereas MHCIIB does not. By contrast, MHCIIB interacts with Lgl1, a member of the Scribble/Dlg/Lgl polarity complex, whereas MHCIIA does not. MHCIIB (-/-) fibroblasts exhibited deregulated endogenous levels of the Par polarity complex members, Par3 and Par6. Together, the data show that MHCIIB deficiency causes imbalances in signalling pathways that are responsible for cell polarity determination. The results suggest that these pathways are targets of MIIB in the regulation of the cell's shape and polarity.

The Arp2/3 Activator WASH Controls the Fission of Endosomes through a Large Multiprotein Complex

The Arp2/3 complex generates branched actin networks when activated by Nucleation Promoting Factors (NPFs). Recently, the WASH family of NPFs has been identified, but its cellular role is unclear. Here, we show that WASH generates an actin network on a restricted domain of sorting and recycling endosomes. We found that WASH belongs to a multiprotein complex containing seven subunits, including the heterodimer of capping protein (CP). In vitro, the purified WASH complex activates Arp2/3-mediated actin nucleation and binds directly to liposomes. WASH also interacts with dynamin. WASH depletion gives rise to long membrane tubules pulled out from endosomes along microtubules, as does dynamin inhibition. Accordingly, WASH is required for efficient transferrin recycling. Together, these data suggest that the WASH molecular machine, integrating CP with a NPF, controls the fission of endosomes through an interplay between the forces generated by microtubule motors and actin polymerization.

Association of Cortactin, Fascin‐1 and Epidermal Growth Factor Receptor (EGFR) Expression in Ovarian Carcinomas: Correlation with Clinicopathological Parameters

Cortactin, fascin-1 and EGFR are recognized as important factors in tumor progression. We tested the hypothesis that cortactin, fascin-1 and EGFR expression correlates with clinicopathological parameters of the four most common ovarian surface epithelial carcinomas – serous cystadenocarcinoma, mucinous cystadenocarcinoma, endometrioid adenocarcinoma, and clear cell carcinoma. Immunohistochemical analysis of cortactin, fascin-1 and EGFR was performed using tissue microarrays of 172 specimens comprising 69 serous cystadenocarcinomas, 44 mucinous cystadenocarcinomas, 45 endometrioid adenocarcinomas and 14 clear cell carcinomas. All ovarian carcinomas showed significant expression of cortactin, fascin-1 and EGFR in staining intensity, tumor percentages and immunostaining scores. In addition, higher immunostaining scores of fascin-1 correlated with more advanced cancer stages (TNM), poorer histological differentiation and poorer survival rate of mucinous cystadenocarcinoma. Similarly, higher immunostaining scores of cortactin correlated with T stages and histological differentiation of serous cystadenocarcinoma. The immunostaining scores of EGFR did not correlate with TNM stages, tumor differentiation or prognosis in the four ovarian surface epithelial carcinomas. Our findings suggest that cortactin and fascin-1 may serve as good biomarkers in evaluating aggressiveness of ovarian serous and mucinous cystadenocarcinoma. And the pharmacological inhibitors of fascin-1 activity may slow down tumor progression and prolong survival time in patients with mucinous cystadenocarcinoma.

Association of Cortactin and Fascin-1 Expression in Gastric Adenocarcinoma: Correlation With Clinicopathological Parameters

Cortactin and fascin-1 are important factors in tumor progression. We tested the hypothesis that cortactin and fascin-1 expression correlates with clinicopathological parameters of gastric adenocarcinoma. Immunohistochemical analysis of cortactin and fascin-1 was done using tissue microarrays of 100 surgical specimens, including 20 well-differentiated, 20 moderately differentiated, and 60 poorly differentiated gastric adenocarcinomas. Among the 20 well-differentiated gastric adenocarcinomas, 15 cases (75%) showed negative or weak staining (1+); 5 cases (25%) had moderate (2+) or strong (3+) cortactin expression. Among the 60 poorly differentiated gastric adenocarcinomas, more than three-quarters of the cases (76.7%) had moderate or strong cortactin expression; 14 cases (23.3%) had weak staining. Of 20 well-differentiated gastric adenocarcinoma cases, 14 (70%) showed negative or weak staining of fascin-1, whereas nearly one-third (30%) had moderate or strong expression. Among the 60 poorly differentiated gastric adenocarcinomas, 32 (53.3%) exhibited moderate or strong fascin-1 expression; fewer than half of the cases showed negative or weak staining. Higher intensity of cortactin and fascin-1 staining correlated directly with more-advanced cancer stages (TNM) and inversely with survival rates. Our findings suggest the possibility that pharmacological inhibitors of cortactin and fascin-1 activity may slow down tumor progression and prolong survival time in patients with gastric adenocarcinomas.

Dual Roles of Tight Junction-associated Protein, Zonula Occludens-1, in Sphingosine 1-Phosphate-mediated Endothelial Chemotaxis and Barrier Integrity

In this report, sphingosine-1-phosphate (S1P), a serum-borne bioactive lipid, is shown to activate tight-junction-associated protein Zonula Occludens-1 (ZO-1), which in turn plays a critical role in regulating endothelial chemotaxis and barrier integrity. After S1P stimulation, ZO-1 was redistributed to the lamellipodia and cell-cell junctions via the S1P1/G(i)/Akt/Rac pathway. Similarly, both endothelial barrier integrity and cell motility were significantly enhanced in S1P-treated cells through the G(i)/Akt/Rac pathway. Importantly, S1P-enhanced barrier integrity and cell migration were abrogated in ZO-1 knockdown cells, indicating ZO-1 is functionally indispensable for these processes. To investigate the underlying mechanisms, we demonstrated that cortactin plays a critical role in S1P-induced ZO-1 redistribution to the lamellipodia. In addition, S1P significantly induced the formation of endothelial tight junctions. ZO-1 and alpha-catenin polypeptides were colocalized in S1P-induced junctional structures; whereas, cortactin was not observed in these regions. Together, these results suggest that S1P induces the formation of two distinct ZO-1 complexes to regulate two different endothelial functions: ZO-1/cortactin complexes to regulate chemotactic response and ZO-1/alpha-catenin complexes to regulate endothelial barrier integrity. The concerted operation of these two ZO-1 complexes may coordinate two important S1P-mediated functions, i.e. migration and barrier integrity, in vascular endothelial cells.

Sequential Interaction of Actin-related Proteins 2 and 3 (Arp2/3) Complex with Neural Wiscott-Aldrich Syndrome Protein (N-WASP) and Cortactin during Branched Actin Filament Network Formation

The WASP and cortactin families constitute two distinct classes of Arp2/3 modulators in mammalian cells. Physical and functional interactions among the Arp2/3 complex, VCA (a functional domain of N-WASP), and cortactin were examined under conditions that were with or without actin polymerization. In the absence of actin, cortactin binds significantly weaker to the Arp2/3 complex than VCA. At concentrations of VCA 20-fold lower than cortactin, the association of cortactin with the Arp2/3 complex was nearly abolished. Analysis of the cells infected with Shigella demonstrated that N-WASP located at the tip of the bacterium, whereas cortactin accumulated in the comet tail. Interestingly, cortactin promotes Arp2/3 complex-mediated actin polymerization and actin branching in the presence of VCA at a saturating concentration, and cortactin acquired 20 nm affinity for the Arp2/3 complex during actin polymerization. The interaction of VCA with the Arp2/3 complex was reduced in the presence of both cortactin and actin. Moreover, VCA reduced its affinity for Arp2/3 complex at branching sites that were stabilized by phalloidin. These data imply a novel mechanism for the de novo assembly of a branched actin network that involves a coordinated sequential interaction of N-WASP and cortactin with the Arp2/3 complex.

Association of cortactin with dynamic actin in lamellipodia and on endosomal vesicles.

We have used fluorescent protein tagging to study the localization and dynamics of the actin-binding protein cortactin in living NIH 3T3 fibroblast cells. Cortactin was localized to active lamellipodia and to small cytoplasmic spots. Time-lapse imaging revealed that these cortactin labeled structures were very dynamic. In the lamellipodia, cortactin labeled structures formed at the leading edge and then moved toward the cell center. Experiments with green fluorescent protein (GFP)-tagged actin showed that cortactin movement was coincident with the actin retrograde flow in the lamellipodia. Cytoplasmic cortactin spots also contained F-actin and were propelled by actin polymerization. Arp3, a component of the arp2/3 complex which is a key regulator of actin polymerization, co-localized with cortactin. Cytoplasmic cortactin-labeled spots were found to be associated with endosomal vesicles. Association was asymmetric and approximately half of the endosomes were associated with cortactin spots. Time-lapse imaging suggested that these cortactin and F-actin-containing spots propelled endosomes. Actin polymerization based propulsion may be a common mechanism for endomembrane trafficking in the same manner as used in the plasma membrane protrusions. As cortactin is known to interact with membrane-associated signaling proteins it could have a role in linking signaling complexes with dynamic actin on endosomes and in lamellipodia.

Association of cortactin with dynamic actin in lamellipodia and on endosomal vesicles

Association of cortactin with dynamic actin in lamellipodia and on endosomal vesicles

Association of cortactin with developing neuromuscular specializations.

During the development of the neuromuscular junction (NMJ), motoneurons grow to the muscle cell and the nerve-muscle contact triggers the development of both presynaptic specialization, consisting of clusters of synaptic vesicles (SVs), and postsynaptic specialization, consisting of clusters of synaptic vesicles (SVs), and postsynaptic specialization, consisting of clusters of acetylcholine receptors (AChRs). Previous studies have shown that the activation of tyrosine kinases and the local assembly of an actin-based cytoskeletal specialization are involved in the development of both types of specializations. To understand the link between tyrosine phosphorylation and the assembly of the cytoskeleton, we examined the localization of cortactin in relationship to synaptic development. Cortactin is a 80/85 kD F-actin binding protein and is a substrate for tyrosine kinases. It contains a proline-rich motif and an SH3 domain and is localized at sites of active F-actin assembly. Using a monoclonal antibody against cortactin, its localization at developing NMJs in culture was observed. To understand the spatial and temporal relationship between cortactin and developing synaptic structures, cultured muscle cells and spinal neurons from Xenopus embryos were treated with beads coated with heparin-binding growth-associated molecule to induce the formation of AChR clusters and SV clusters and the localization of cortactin was followed by immunofluorescence. In untreated muscle cells, cortactin is often co-localized with spontaneously formed AChR clusters. After cells were treated with beads, cortactin became localized at bead-induced AChR clusters at their earliest appearance (1 h after the addition of beads). This association was most reliably detected at the early stage of the clustering process. On the presynaptic side, cortactin localization could be detected as early as 10 min after the bead-neurite contact was established. Cortactin-enriched contacts later showed concentration of F-actin (at 1 h) and clusters of SVs (at 24 h). These data suggest that cortactin mediates the local assembly of the cytoskeletal specialization triggered by the synaptogenic signal on both nerve and muscle.