The phosphatase Shp1 interacts with and dephosphorylates cortactin to inhibit invadopodia function

BACKGROUND

Invadopodia are actin-based cell-membrane protrusions associated with the extracellular matrix degradation accompanying cancer invasion. The elucidation of the molecular mechanisms leading to invadopodia formation and activity is central for the prevention of tumor spreading and growth. Protein tyrosine kinases such as Src are known to regulate invadopodia assembly, little is however known on the role of protein tyrosine phosphatases in this process. Among these enzymes, we have selected the tyrosine phosphatase Shp1 to investigate its potential role in invadopodia assembly, due to its involvement in cancer development.

METHODS

Co-immunoprecipitation and immunofluorescence studies were employed to identify novel substrate/s of Shp1AQ controlling invadopodia activity. The phosphorylation level of cortactin, the Shp1 substrate identified in this study, was assessed by immunoprecipitation, in vitro phosphatase and western blot assays. Short interference RNA and a catalytically-dead mutant of Shp1 expressed in A375MM melanoma cells were used to evaluate the role of the specific Shp1-mediated dephosphorylation of cortactin. The anti-invasive proprieties of glycerophosphoinositol, that directly binds and regulates Shp1, were investigated by extracellular matrix degradation assays and in vivo mouse model of metastasis.

RESULTS

The data show that Shp1 was recruited to invadopodia and promoted the dephosphorylation of cortactin at tyrosine 421, leading to an attenuated capacity of melanoma cancer cells to degrade the extracellular matrix. Controls included the use of short interference RNA and catalytically-dead mutant that prevented the dephosphorylation of cortactin and hence the decrease the extracellular matrix degradation by melanoma cells. In addition, the phosphoinositide metabolite glycerophosphoinositol facilitated the localization of Shp1 at invadopodia hence promoting cortactin dephosphorylation. This impaired invadopodia function and tumor dissemination both in vitro and in an in vivo model of melanomas.

CONCLUSION

The main finding here reported is that cortactin is a specific substrate of the tyrosine phosphatase Shp1 and that its phosphorylation/dephosphorylation affects invadopodia formation and, as a consequence, the ability of melanoma cells to invade the extracellular matrix. Shp1 can thus be considered as a regulator of melanoma cell invasiveness and a potential target for antimetastatic drugs. Video abstract.

Autoantibodies to cortactin and agrin in sera of patients with myasthenia gravis

Autoantibodies against agrin and cortactin have been described in patients with myasthenia gravis. To further validate and characterize these autoantibodies, sera and/or plasma exchange material of 135 patients with myasthenia gravis were screened for anti-agrin or anti-cortactin autoantibodies. Autoantibodies against cortactin were detected in three patients and two controls and could be confirmed by cell-based assays using cortactin-transfected human embryonic kidney cells in both controls and one patient, but were not detectable in follow-up sera of the three patients. We did not detect any autoantibodies against agrin. The clinical phenotype of anti-cortactin-positive patients varied, arguing against a relevant pathogenic role.

Recruitment of Polarity Complexes and Tight Junction Proteins to the Site of Apical Bulk Endocytosis

BACKGROUND & AIMS

The molecular motor, Myosin Vb (MYO5B), is well documented for its role in trafficking cargo to the apical membrane of epithelial cells. Despite its involvement in regulating apical proteins, the role of MYO5B in cell polarity is less clear. Inactivating mutations in MYO5B result in microvillus inclusion disease (MVID), a disorder characterized by loss of key apical transporters and the presence of intracellular inclusions in enterocytes. We previously identified that inclusions in Myo5b knockout (KO) mice form from invagination of the apical brush border via apical bulk endocytosis. Herein, we sought to elucidate the role of polarity complexes and tight junction proteins during the formation of inclusions.

METHODS

Intestinal tissue from neonatal control and Myo5b KO littermates was analyzed by immunofluorescence to determine the localization of polarity complexes and tight junction proteins.

RESULTS

Proteins that make up the apical polarity complexes-Crumbs3 and Pars complexes-were associated with inclusions in Myo5b KO mice. In addition, tight junction proteins were observed to be concentrated over inclusions that were present at the apical membrane of Myo5b-deficient enterocytes in vivo and in vitro. Our mouse findings are complemented by immunostaining in a large animal swine model of MVID genetically engineered to express a human MVID-associated mutation that shows an accumulation of Claudin-2 over forming inclusions. The findings from our swine model of MVID suggest that a similar mechanism of tight junction accumulation occurs in patients with MVID.

CONCLUSIONS

These data show that apical bulk endocytosis involves the altered localization of apical polarity proteins and tight junction proteins after loss of Myo5b.

Profiling the expression of pro-metastatic genes in association with the clinicopathological features of primary breast cancer

BACKGROUND

Metastasis accounts for ninety percent of breast cancer (BrCa) mortality. Cortactin, Ras homologous gene family member A (RhoA), and Rho-associated kinase (ROCK) raise cellular motility in favor of metastasis. Claudins (CLDN) belong to tight junction integrity and are dysregulated in BrCa. Thus far, epidemiologic evidence regarding the association of different pro-metastatic genes with pathological phenotypes of BrCa is largely inconsistent. This study aimed to determine the possible transcriptional models of pro-metastatic genes incorporate in holding the integrity of epithelial cell-cell junctions (CTTN, RhoA, ROCK, CLDN-1, CLDN-2, and CLDN-4), for the first time, in association with clinicopathological features of primary BrCa.

METHODS

In a consecutive case-series design, 206 newly diagnosed non-metastatic eligible BrCa patients with histopathological confirmation (30-65 years) were recruited in Tabriz, Iran (2015-2017). Real-time RT-PCR was used. Then fold changes in the expression of target genes were measured.

RESULTS

ROCK amplification was associated with the involvement of axillary lymph node metastasis (ALNM; ORadj. = 3.05, 95%CI 1.01-9.18). Consistently, inter-correlations of CTTN-ROCK (β = 0.226, P < 0.05) and RhoA-ROCK (β = 0.311, P < 0.01) were determined among patients diagnosed with ALNM+ BrCa. In addition, the overexpression of CLDN-4 was frequently observed in tumors identified by ALNM+ or grade III (P < 0.05). The overexpression of CTTN, CLDN-1, and CLDN-4 genes was correlated positively with the extent of tumor size. CTTN overexpression was associated with the increased chance of luminal-A positivity vs. non-luminal-A (ORadj. = 1.96, 95%CI 1.02-3.77). ROCK was also expressed in luminal-B BrCa tumors (P < 0.05). The estrogen receptor-dependent transcriptions were extended to the inter-correlations of RhoA-ROCK (β = 0.280, P < 0.01), ROCK-CLDN-2 (β = 0.267, P < 0.05), and CLDN-1-CLDN-4 (β = 0.451, P < 0.001).

CONCLUSIONS

For the first time, our findings suggested that the inter-correlations of CTTN-ROCK and RhoA-ROCK were significant transcriptional profiles determined in association with ALNM involvement; therefore the overexpression of ROCK may serve as a potential molecular marker for lymphatic metastasis. The provided binary transcriptional profiles need more approvals in different clinical features of BrCa metastasis.

Autism-linked mutations of CTTNBP2 reduce social interaction and impair dendritic spine formation via diverse mechanisms

Abnormal synaptic formation and signaling is one of the key molecular features of autism spectrum disorders (ASD). Cortactin binding protein 2 (CTTNBP2), an ASD-linked gene, is known to regulate the subcellular distribution of synaptic proteins, such as cortactin, thereby controlling dendritic spine formation and maintenance. However, it remains unclear how ASD-linked mutations of CTTNBP2 influence its function. Here, using cultured hippocampal neurons and knockin mouse models, we screen seven ASD-linked mutations in the short form of the Cttnbp2 gene and identify that M120I, R533* and D570Y mutations impair CTTNBP2 protein-protein interactions via divergent mechanisms to reduce dendritic spine density in neurons. R533* mutation impairs CTTNBP2 interaction with cortactin due to lack of the C-terminal proline-rich domain. Through an N-C terminal interaction, M120I mutation at the N-terminal region of CTTNBP2 also negatively influences cortactin interaction. D570Y mutation increases the association of CTTNBP2 with microtubule, resulting in a dendritic localization of CTTNBP2, consequently reducing the distribution of CTTNBP2 in dendritic spines and impairing the synaptic function of CTTNBP2. Finally, we generated heterozygous M120I knockin mice to mimic the genetic variation of patients and found they exhibit reduced social interaction. Our study elucidates that different ASD-linked mutations of CTTNBP2 result in diverse molecular deficits, but all have the similar consequence of synaptic impairment.

Inhibition of invadopodia formation by diosgenin in tumor cells

Diosgenin is a type of steroid extracted from the rhizome of Dioscorea plants. In traditional Chinese medicine, Dioscorea has the effect of ‘eliminating phlegm, promoting digestion, relaxing tendons, promoting blood circulation and inhibiting malaria’. Recent studies have confirmed that diosgenin exhibits a number of pharmacological effects, including antitumor activities. Through its antitumor effect, diosgenin is able to block tumor progression and increase the survival rate of patients with cancer; ultimately improving their quality of life. However, the mechanism underlying its pharmacological action remains unclear. Once tumor cells reach a metastatic phase, it can be fatal. Increased migration and invasiveness are the hallmarks of metastatic tumor cells. Invadopodia formation is key to maintaining the high migration and invasive ability of tumor cells. Invadopodia are a type of membrane structure process rich in filamentous-actin and are common in highly invasive tumor cells. In addition to actin, numerous actin regulators, including cortical actin-binding protein (Cortactin), accumulate in invadopodia. Cortactin is a microfilament actin-binding protein with special repetitive domains that are directly involved in the formation of the cortical microfilament actin cell skeleton. Cortactin is also one of the main substrates of intracellular Src-type tyrosine protein kinases and represents a highly conserved family of intracellular cortical signaling proteins. In recent years, great progress has been made in understanding the role of Cortactin and its molecular mechanism in cell motility. However, the diosgenin-Cortactin-invadopodia mechanism is still under investigation. Therefore, the present review focused on the current research on the regulation of invadopodia by diosgenin via Cortactin.

Quantitative acetylome and phosphorylome analysis reveals Girdin affects pancreatic cancer progression through regulating Cortactin

The actin-binding protein Girdin is involved in a variety of cellular processes, including pancreatic cancer. The objective of this study is to explore the role and the mechanism of Girdin in pancreatic cancer by quantitative acetylome and phosphorylome analysis. We firstly found that Girdin was overexpressed in pancreatic cancer tissue and increased expression of Girdin was associated with tumor size and stage of patients with pancreatic cancer. We established the shRNA knockdown of Girdin in PANC-1 and Aspc-1 cells, and we found that shGirdin inhibited proliferation, migration and invasion, and promoted apoptosis. Subsequently, we identified and quantified 5,338 phosphorylated sites in 2,263 proteins that changed in response to Girdin knockdown, and identified a similar set of Girdin-responsive acetylome data as well. Additional data revealed that down-regulation of Girdin affected Cortactin phosphorylation and acetylation, suggesting Cortactin as an important regulatory target of Girdin. Moreover, we found that overexpression of Cortactin could rescue the effect of shGirdin on proliferation, apoptosism, migration and invasion of pancreatic cancer cells. In general, our results provided new insights into the mechanisms of Girdin function including cell proliferation, migration and invasion, and offer biomarker candidates for clinical evaluation of Girdin.

Arg kinase mediates CXCL12/CXCR4-induced invadopodia formation and invasion of glioma cells

Compared with noninvasive tumor cells, glioma cells overexpress chemokine receptor type 4 (CXCR4), which exhibits significantly greater expression in invasive tumor cells than in noninvasive tumor cells. C-X-C motif chemokine ligand 12 (CXCL12, also known as stromal derived factor-1, SDF-1) and its cell surface receptor CXCR4 activate a signaling axis that induces the expression of membrane type-2 matrix metalloproteinase (MT2-MMP), which plays a pivotal role in the invasion and migration of various cancer cells; however, the specific mechanism involved in this is unclear. Recently, studies have shown that invadopodia can recruit and secrete related enzymes, such as matrix metalloproteinases (MMPs), to degrade the surrounding extracellular matrix (ECM), promoting the invasion and migration of tumor cells. Phosphorylated cortactin (pY421-cortactin) is required for the formation and maturation of invadopodia, but the upstream regulatory factors and kinases involved in phosphorylation have not been elucidated. In this study, we found that CXCL12/CXCR4 was capable of inducing glioma cell invadopodia formation, probably by regulating cortactin phosphorylation. The interaction of cortactin and Arg (also known as Abl-related nonreceptor tyrosine kinase, ABL2) in glioma cells was demonstrated. The silencing of Arg inhibited glioma cell invadopodia formation and invasion by blocking cortactin phosphorylation. Moreover, CXCL12 could not induce glioma cell invasion in Arg-knockdown glioma cells. Based on these results, it can be concluded that Arg mediates CXCL12/CXCR4-induced glioma cell invasion, and CXCL12/CXCR4 regulates invadopodia maturation through the Arg-cortactin pathway, which indicates that Arg could be a candidate therapeutic target to inhibit glioma cell invasion.

CD44 mediates stem cell mobilization to damaged lung via its novel transcriptional targets, Cortactin and Survivin

Beyond their role in bone and lung homeostasis, mesenchymal stem cells (MSCs) are becoming popular in cell therapy. Various insults may disrupt the repair mechanisms involving MSCs. One such insult is smoking, which is a major risk factor for osteoporosis and respiratory diseases. Upon cigarette smoke-induced damage, a series of reparatory mechanisms ensue; one such mechanism involves Glycosaminoglycans (GAG). One of these GAGs, namely hyaluronic acid (HA), serves as a potential therapeutic target in lung injury. However, much of its mechanisms of action through its major receptor CD44 remains unexplored. Our previous studies have identified and functionally validated that both cortactin (CTTN: marker of motility) and Survivin (BIRC5: required for cell survival) act as novel HA/CD44-downstream transcriptional targets underpinning cell motility. Here, human MSCs were treated with "Water-pipe" smoke to investigate the effects of cigarette smoke condensate (CSC) on these HA-CD44 novel signaling pathways. Our results show that CSC decreased the expression of both CD44 and its downstream targets CTTN and BIRC5 in MSCs, and that HA reversed these effects. Interestingly, CSC inhibited migration and invasion of MSCs upon CD44-targeted RNAi treatment. This shows the importance of CD44-HA/CTTN and CD44-HA/BIRC5 signaling pathways in MSC motility, and further suggests that these signaling pathways may provide a novel mechanism implicated in migration of MSCs during repair of lung tissue injury. These findings suggest that one should use caution before utilizing MSC from donors with history of smoking, and further pave the way towards the development of targeted therapeutic approaches against CD44-associated diseases.

Rapid Estrogen and Progesterone Signaling to Dendritic Spine Formation via Cortactin/Wave1-Arp2/3 Complex

BACKGROUND

Synaptic plasticity is the neuronal capacity to modify the function and structure of dendritic spines (DS) in response to neuromodulators. Sex steroids, particularly 17β-estradiol (E2) and progesterone (P4), are key regulators in the control of DS formation through multiprotein complexes including WAVE1 protein, and are thus fundamental for the development of learning and memory.

OBJECTIVES

The aim of this work was to evaluate the molecular switch Cdk5 kinase/protein phosphatase 2A (PP2A) in the control of WAVE1 protein (phosphorylation/dephosphorylation) and the regulation of WAVE1 and cortactin to the Arp2/3 complex, in response to rapid treatments with E2 and P4 in cortical neuronal cells.

RESULTS

Rapid treatment with E2 and P4 modified neuronal morphology and significantly increased the number of DS. This effect was reduced by the use of a Cdk5 inhibitor (Roscovitine). In contrast, inhibition of PP2A with PP2A dominant negative construct significantly increased DS formation, evidencing the participation of kinase/phosphatase in the regulation of WAVE1 in DS formation induced by E2 and P4. Cortactin regulates DS formation via Src and PAK1 kinase induced by E2 and P4. Both cortactin and WAVE1 signal to Arp2/3 complex to synergistically promote actin nucleation.

CONCLUSION

These results suggest that E2 and P4 dynamically regulate neuron morphology through nongenomic signaling via cortactin/WAVE1-Arp2/3 complex. The control of these proteins is tightly orchestrated by phosphorylation, where kinases and phosphatases are essential for actin nucleation and, finally, DS formation. This work provides a deeper understanding of the biological actions of sex steroids in the regulation of DS turnover and neuronal plasticity processes.

Concerted regulation of actin polymerization during constitutive secretion by cortactin and PKD2

Constitutive secretion from the trans-Golgi-network (TGN) is facilitated by a concerted regulation of vesicle biogenesis and fission processes. The protein kinase D family (PKD) has been previously described to enhance vesicle fission by modifying the lipid environment. PKD also phosphorylates the actin regulatory protein cortactin at S298 to impair synergistic actin polymerization. We here report additional functions for PKD2 (also known as PRKD2) and cortactin in the regulation of actin polymerization during the fission of transport carriers from the TGN. Phosphorylation of cortactin at S298 impairs the interaction between WIP (also known as WIPF1) and cortactin. WIP stabilizes the autoinhibited conformation of N-WASP (also known as WASL). This leads to an inhibition of synergistic Arp2/3-complex-dependent actin polymerization at the TGN. PKD2 activity at the TGN is controlled by active CDC42-GTP which directly activates N-WASP, inhibits PKD2 and shifts the balance to non-S298-phosphorylated cortactin, which can in turn sequester WIP from N-WASP. Consequently, synergistic actin polymerization at the TGN and constitutive secretion are enhanced.

Cellular and pathophysiological consequences of Arp2/3 complex inhibition: role of inhibitory proteins and pharmacological compounds

The actin-related protein complex 2/3 (Arp2/3) generates branched actin networks important for many cellular processes such as motility, vesicular trafficking, cytokinesis, and intercellular junction formation and stabilization. Activation of Arp2/3 requires interaction with actin nucleation-promoting factors (NPFs). Regulation of Arp2/3 activity is achieved by endogenous inhibitory proteins through direct binding to Arp2/3 and competition with NPFs or by binding to Arp2/3-induced actin filaments and disassembly of branched actin networks. Arp2/3 inhibition has recently garnered more attention as it has been associated with attenuation of cancer progression, neurotoxic effects during drug abuse, and pathogen invasion of host cells. In this review, we summarize current knowledge on expression, inhibitory mechanisms and function of endogenous proteins able to inhibit Arp2/3 such as coronins, GMFs, PICK1, gadkin, and arpin. Moreover, we discuss cellular consequences of pharmacological Arp2/3 inhibition.

Muscle-Specific Tyrosine Kinase and Myasthenia Gravis Owing to Other Antibodies

Around 20% of patients with myasthenia gravis are acetylcholine receptor antibody negative; muscle-specific tyrosine kinase antibodies (MuSK) were identified as the cause of myasthenia gravis in 30% to 40% of these cases. Anti MuSK myasthenia gravis is associated with specific clinical phenotypes. One is a bulbar form with fewer ocular symptoms. Others show an isolated head drop or symptoms indistinguishable from acetylcholine receptor-positive myasthenia gravis. These patients usually respond well to immunosuppressive therapy, but not as well to cholinesterase inhibitors. Other antibodies associated with myasthenia gravis, including low-density lipoprotein receptor-related protein 4, are discussed.

The Drosophila protein, Nausicaa, regulates lamellipodial actin dynamics in a Cortactin-dependent manner

Drosophila CG10915 is an uncharacterized protein coding gene with sequence similarity to human Cortactin-binding protein 2 (CTTNBP2) and Cortactin-binding protein 2 N-terminal-like (CTTNBP2NL). Here, we have named this gene Nausicaa (naus) and characterize it through a combination of quantitative live-cell total internal reflection fluorescence microscopy, electron microscopy, RNAi depletion and genetics. We found that Naus co-localizes with F-actin and Cortactin in the lamellipodia of Drosophila S2R+ and D25c2 cells and this localization is lost following Cortactin or Arp2/3 depletion or by mutations that disrupt a conserved proline patch found in its mammalian homologs. Using permeabilization activated reduction in fluorescence and fluorescence recovery after photobleaching, we find that depletion of Cortactin alters Naus dynamics leading to a decrease in its half-life. Furthermore, we discovered that Naus depletion in S2R+ cells led to a decrease in actin retrograde flow and a lamellipodia characterized by long, unbranched filaments. We demonstrate that these alterations to the dynamics and underlying actin architecture also affect D25c2 cell migration and decrease arborization in Drosophila neurons. We present the hypothesis that Naus functions to slow Cortactin's disassociation from Arp2/3 nucleated branch junctions, thereby increasing both branch nucleation and junction stability.

The Pathogenic Effect of Cortactin Tyrosine Phosphorylation in Cutaneous Squamous Cell Carcinoma

BACKGROUND/AIM

Cortactin (CTTN) has been considered a promising molecular prognostic factor in various types of cancers. In this study, we aimed to investigate the role of CTTN in the pathogenesis of cutaneous squamous cell carcinoma (CSCC).

MATERIALS AND METHODS

CTTN and phospho-CTTN (p-CTTN) expression was determined in 10 healthy controls and 38 CSCC tissue samples by immunohistochemistry. The influence of CTTN on the biological behavior of CSCC cells was also investigated.

RESULTS

p-CTTN expression was significantly increased in CSCC than control samples. In contrast, no significant difference in CTTN expression was found between control and CSCC tissues. Moreover, a significant association was found between recurrence-free survival with p-CTTN expression, but not with CTTN expression. Furthermore, the proliferative, migratory, and invasive abilities of CSCC cells were significantly decreased by CTTN-siRNA transfection.

CONCLUSION

CTTN phosphorylation is strongly associated with CSCC pathogenesis and may serve as a molecular biomarker of CSCC.

Keratinocyte growth factor (KGF) induces podosome formation via integrin-Erk1/2 signaling in human immortalized oral epithelial cells

Recent study established the role of integrins in keratinocyte growth factor (KGF)-induced oral epithelial adhesion and rete peg elongation. However, how extracellular matrix (ECM) remodeling cooperates with the increased epithelial adhesion during rete peg elongation has yet to be determined. Podosomes are cell-matrix contact structures that combine several abilities, including adhesion and matrix degradation. In the present study, we identified podosome formation at the ventral side of human immortalized oral epithelial cells (HIOECs) upon KGF treatment. Moreover, podosomal components including integrin α6，β4，α3，β1 and MMP14 colocalized with the F-actin-cortactin complex and matrix degradation assays demonstrated the ability of the F-actin-cortactin complex to degrade matrix. Inhibition both of integrin subunits β4 and β1 with specific blocking antibodies and inhibition of Erk1/2 abrogated the KGF-induced podosome formation. Notably, knockdown of integrin subunits β4 and β1 with specific small interfering RNA (siRNA) downregulated the phosphorylation levels of Erk1/2. In contrast, inhibition of both Erk1/2 could upregulate the expression of integrin subunits β4 and β1. These results demonstrate that KGF induces podosome formation via integrin-Erk1/2 signaling in HIOECs, suggesting a novel mechanism by which integrins enhance oral epithelial adhesion and rete peg elongation.

Overexpression and Tyr421-phosphorylation of cortactin is induced by three-dimensional spheroid culturing and contributes to migration and invasion of pancreatic ductal adenocarcinoma (PDAC) cells

BACKGROUND

The nucleation-promoting factor cortactin is expressed and promotes tumor progression and metastasis in various cancers. However, little is known about the biological role of cortactin in the progression of pancreatic ductal adenocarcinoma (PDAC).

METHODS

Cortactin and phosphorylated cortactin (Y421) were investigated immunohistochemically in 66 PDAC tumor specimens. To examine the functional role of cortactin in PDAC, we modulated cortactin expression by establishing two cortactin knockout cell lines (Panc-1 and BxPC-3) with CRISPR/Cas9 technique. Cortactin knockout was verified by immunoblotting and immunofluorescence microscopy and functional effects were determined by cell migration and invasion assays. A proteomic screening approach was performed to elucidate potential binding partners of cortactin.

RESULTS

Immunohistochemically, we observed higher cortactin expression and Tyr421-phosphorylation in PDAC metastases compared to primary tumor tissues. In PDAC cell lines Panc-1 and BxPC-3, knockdown of cortactin impaired migration and invasion, while cell proliferation was not affected. Three-dimensional spheroid culturing as a model for collective cell migration enhanced cortactin expression and Tyr421-phosphorylation. The activation of cortactin as well as the migratory capacity of PDAC cells could significantly be reduced by dasatinib, a Src family kinase inhibitor. Finally, we identified gelsolin as a novel protein interaction partner of cortactin in PDAC.

CONCLUSION

Our data provides evidence that cohesive cell migration induces cortactin expression and phosphorylation as a prerequisite for the gain of an invasive, pro-migratory phenotype in PDAC that can effectively be targeted with dasatinib.

Arp2/3-branched actin regulates microtubule acetylation levels and affects mitochondrial distribution

Actin and microtubule cytoskeletons regulate cell morphology, participate in organelle trafficking and function in response to diverse environmental cues. Precise spatial-temporal coordination between these two cytoskeletons is essential for cells to live and move. Here, we report a novel crosstalk between actin and microtubules, in which the branched actin maintains microtubule organization, dynamics and stability by affecting tubulin acetylation levels. We observed that acetylated tubulin significantly decreases upon perturbation of the Arp2/3-branched actin. We subsequently discover that HDAC6 participates in this process by altering its interaction with tubulin and the Arp2/3-stabilizer cortactin. We further identify that the homeostasis of branched actin controls mitochondrial distribution via this microtubule acetylation-dependent mechanism. Our findings shed new light on the integral view of cytoskeletal networks, highlighting post-translational modification as another possible form of cytoskeletal inter-regulation, aside from the established crosstalks through structural connection or upstream signaling pathways.

ATM-Mediated Phosphorylation of Cortactin Involved in Actin Polymerization Promotes Breast Cancer Cells Migration and Invasion

BACKGROUND/AIMS

The ataxia-telangiectasia mutated (ATM) protein kinase is critical for the maintenance of genomic stability and acts as tumor suppressor. Although evidence shows that a DNA damage-independent ATM (oxidized ATM) may be involved in cancer progression, the underlying mechanism is still unclear.

METHODS

Immunohistochemistry, immunofluorescence and western blotting were applied to detect the levels of oxidized ATM. Transwell assay was used to detect the cell migration and invasion abilities in different treatments. Quantitative phosphoproteome analysis was performed using hypoxic BT549 cells, in the presence or absence of Ku60019, a specific inhibitor of ATM kinase. The phosphorylated cortactin, the target protein of oxidized ATM, was confirmed by immunoprecipitation-western blots and in vitro kinase assay. The functions of phosphorylated cortactin were studied by specific short hairpin RNA, site-directed mutation, transwell assay, and actin polymerization assay.

RESULTS

Enhanced oxidized ATM proteins were present not only in the advanced and invasive breast tumor tissues but also malignant hypoxic breast cancer cells, in the absence of DNA damage. Loss of ATM expression or inhibiting oxidized ATM kinase activity reduced breast cancer cell migration and invasion. Using quantitative phosphoproteomics approach, 333 oxidized ATM target proteins were identified, some of these proteins govern key signaling associated with gap junction, focal adhesion, actin cytoskeleton rearrangement. Cortactin, one of the biggest changed phospho-protein, is a novel oxidized ATM-dependent target in response to hypoxia. Mechanically, we reveal that hypoxia-activated ATM can enhance the binding affinity of cortactin with Arp2/3 complex by phosphorylating cortactin at serine 113, and as a result, in favor of breast cancer cell migration and invasion.

CONCLUSION

Oxidized ATM can phosphorylate cortactin at serine 113, playing a critical role in promoting breast tumor cell mobility and invasion via actin polymerization.

Cortactin expression in non-Hodgkin B-cell lymphomas: a new marker for the differential diagnosis between chronic lymphocytic leukemia and mantle cell lymphoma

Cortactin is a cytoskeletal-remodeling adaptor protein, playing an oncogenic role in solid tumors. Little is known on cortactin expression in non-Hodgkin B-cell lymphomas (B-NHLs). The present study aimed to characterize cortactin expression in B-NHLs and to assess its role in the differential diagnosis of such entities. Cortactin protein expression was first assessed by immunohistochemistry in a series of 131 B-NHLs, including B-cell chronic lymphocytic leukemia (CLL; n = 17), mantle cell lymphoma (MCL; n = 16), follicular lymphoma (FL; n = 25), marginal zone lymphoma (MZL; n = 30), hairy cell leukemia (HCL; n = 10), splenic diffuse red pulp small B-cell lymphomas (SDRPBL; n = 3), and diffuse large B-cell lymphoma (DLBCL; n = 30) cases. Cortactin was expressed in 14 of 17 CLLs, 10 of 10 HCLs, and 22 of 30 DLBCLs. MCLs, SDRPBLs, most FLs, and MZLs were cortactin negative. The immunohistochemical results were in keeping with in silico gene expression data. In CLL, cortactin positivity did correlate with LEF1 and CD200 expression, and the combined positivity for ≥2 markers strongly predicted CLL diagnosis. Such preliminary data suggested a role for cortactin in the differential diagnosis between CLL and MCL. This hypothesis was confirmed in a large validation set of 112 CLLs (n = 55) and MCLs (n = 57), which also disclosed rare cortactin-expressing MCLs. The immunohistochemical and gene expression results were sustained by flow cytometry and Western blot analysis on CLL and MCL cell lines. In conclusion, cortactin is mainly expressed in subsets of CLL and DLBCL and in HCL. Cortactin may represent a novel marker for the differential diagnosis between CLL and MCL.

TKS5-positive invadopodia-like structures in human tumor surgical specimens

Invadopodia, cancer cell protrusions with proteolytic activity, are functionally associated with active remodeling of the extracellular matrix. Here, we show that the invadopodia-related protein TKS5 is expressed in human pancreatic adenocarcinoma lines, and demonstrate that pancreatic cancer cells depend on TKS5 for invadopodia formation and function. Immunofluorescence staining of human pancreatic cancer cells reveals that TKS5 is a marker of mature and immature invadopodia. We also analyze the co-staining patterns of TKS5 and the commonly used invadopodia marker Cortactin, and find only partial co-localization of these two proteins at invadopodia, with a large fraction of TKS5-positive invadopodia lacking detectable levels of Cortactin. Whereas compelling evidence exist on the role of invadopodia as mediators of invasive migration in cultured cells and in animal models of cancer, these structures have never been detected inside human tumors. Here, using antibodies against TKS5 and Cortactin, we describe for the first time structures strongly resembling invadopodia in various paraffin-embedded human tumor surgical specimens from pancreas and other organs. Our results strongly suggest that invadopodia are present inside human tumors, and warrants further investigation on their regulation and occurrence in surgical specimens, and on the value of TKS5 antibodies as pathological research and diagnostic tools.

Cortical Actin Dynamics in Endothelial Permeability

The pulmonary endothelial cell forms a critical semi-permeable barrier between the vascular and interstitial space. As part of the blood-gas barrier in the lung, the endothelium plays a key role in normal physiologic function and pathologic disease. Changes in endothelial cell shape, defined by its plasma membrane, determine barrier integrity. A number of key cytoskeletal regulatory and effector proteins including non-muscle myosin light chain kinase, cortactin, and Arp 2/3 mediate actin rearrangements to form cortical and membrane associated structures in response to barrier enhancing stimuli. These actin formations support and interact with junctional complexes and exert forces to protrude the lipid membrane to and close gaps between individual cells. The current knowledge of these cytoskeletal processes and regulatory proteins are the subject of this review. In addition, we explore novel advancements in cellular imaging that are poised to shed light on the complex nature of pulmonary endothelial permeability.

Histone deacetylase 6 in cancer

Histone acetylation and deacetylation are important epigenetic mechanisms that regulate gene expression and transcription. Histone deacetylase 6 (HDAC6) is a unique member of the HDAC family that not only participates in histone acetylation and deacetylation but also targets several nonhistone substrates, such as α-tubulin, cortactin, and heat shock protein 90 (HSP90), to regulate cell proliferation, metastasis, invasion, and mitosis in tumors. Furthermore, HDAC6 also upregulates several critical factors in the immune system, such as program death receptor-1 (PD-1) and program death receptor ligand-1 (PD-L1) receptor, which are the main targets for cancer immunotherapy. Several selective HDAC6 inhibitors are currently in clinical trials for cancer treatment and bring hope for patients with malignant tumors. A fuller understanding of HDAC6 as a critical regulator of many cellular pathways will help further the development of targeted anti-HDAC6 therapies. Here, we review the unique features of HDAC6 and its role in cancer, which make HDAC6 an appealing drug target.

Cortactin as a potential predictor of second esophageal neoplasia in hypopharyngeal carcinoma

OBJECTIVE

Hypopharyngeal carcinoma has a very poor prognosis. The high incidence of second esophageal neoplasia is one of the major causes. To establish an efficient follow-up scheme for increasing the diagnostic yield and reducing the adverse impact of second esophageal neoplasia on survival, the purpose of this study was to explore a biomarker to predict second esophageal neoplasia.

METHODS

In this retrospective cohort study, consecutive tissue specimens from those patients who underwent tumor resection between September 2007 and October 2015 were collected. Gene amplification was performed by real-time PCR. The expression of cortactin was evaluated by immunohistochemistry. The predictive risk factors of developing second esophageal neoplasia and prognostic factors related to survival were analyzed.

RESULTS

A total of 187 patients were included with a mean follow-up of 48months (12-118months). Second esophageal tumors were found in 53 (28.3%), including 41 (21.9%) esophageal squamous cell carcinoma and 12 severe dysplasia. The results of multivariate analyses revealed that age (OR 2.81, 95% CI 1.16-6.78), cortactin overexpression (OR 2.49, 95% CI 1.17-5.33), and stage IV versus I (OR 6.49, 95% CI 1.68-25.18) were independent predictors of second esophageal neoplasia, and second esophageal neoplasia (HR 1.78, 95% CI 1.05-3.01) was an independent predictor of overall survival.

CONCLUSION

This is the first report to identify a potential biomarker for predicting second esophageal neoplasia in patients with hypopharyngeal carcinoma. In those patients with cortactin overexpression and younger age (≤60years old), close surveillance for second esophageal neoplasia is required. In addition, the real effect of cortactin overexpression on development of primary esophageal carcinoma is required to be validated in a large cohort study.

miR-182 suppresses invadopodia formation and metastasis in non-small cell lung cancer by targeting cortactin gene

Background

Metastasis is the leading cause of cancer mortality and is a major hurdle for lung cancer treatment. Invadopodia, which are cancer-specific protrusive structures, play a crucial role in the metastatic cascade through degradation of the basement membrane and surrounding stroma. Cortactin, a critical component of invadopodia, frequently used as an invadopodia marker, a universally important player in invadopodia function, and is frequently overexpressed in cancer, but the exact mechanism of regulation is not yet fully understood.

Methods

The expression level of CTTN in human non-small cell lung cancer (NSCLC) tissues was detected by qRT-PCR. Cell migration, invasion and invadopodia formation were assessed in vitro by wound-healing, transwell assay and immunofluorescence, respectively. The dual-luciferase reporter assay was used to identify the direct target of miR-182.

Results

Hepatocyte growth factor (HGF) and phorbol 12,13-dibutyrate (PDBu) can induce CTTN expression, motility, and invasion ability, as well as invadopodia formation in non-small cell lung cancer (NSCLC). Moreover, miR-182 suppressed metastasis and invadopodia formation by targeting CTTN in NSCLC. Our qRT-PCR results showed that CTTN expression was inversely correlated with miR-182 expression that suppressed invadopodia formation via suppression of the Cdc42/N-WASP pathway. Furthermore, miR-182 negatively regulated invadopodia function, and suppressed extracellular matrix(ECM) degradation in lung cancer cells by inhibiting cortactin.

Conclusion

Collectively, our results demonstrated that miR-182 targeted CTTN gene in NSCLC and suppressed lung cancer invadopodia formation, and thus suppressed lung cancer metastasis. This suggests a therapeutic application of miR-182 in NSCLC.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0824-1) contains supplementary material, which is available to authorized users.