Reversible silencing of endogenous receptors in intact brain tissue using 2-photon pharmacology.

The physiological activity of proteins is often studied with loss-of-function genetic approaches, but the corresponding phenotypes develop slowly and can be confounding. Photopharmacology allows direct, fast, and reversible control of endogenous protein activity, with spatiotemporal resolution set by the illumination method. Here, we combine a photoswitchable allosteric modulator (alloswitch) and 2-photon excitation using pulsed near-infrared lasers to reversibly silence metabotropic glutamate 5 (mGlu5) receptor activity in intact brain tissue. Endogenous receptors can be photoactivated in neurons and astrocytes with pharmacological selectivity and with an axial resolution between 5 and 10 µm. Thus, 2-photon pharmacology using alloswitch allows investigating mGlu5-dependent processes in wild-type animals, including synaptic formation and plasticity, and signaling pathways from intracellular organelles.

Health promotion in secondary schools: participatory process for constructing a self-assessment tool.

This article presents the process of constructing an effective self-assessment tool for monitoring health promotion in secondary schools (SS). The ultimate aim is to improve adolescents' well-being and quality of life in their reference environment. The design and validation of the instrument were based on participatory action research (involving students, professors, parents, health professionals, youth workers, youth directors, youth managers). A mixed quantitative and qualitative approach was adopted. The construction process included the following five consecutive stages: (i) steering-group creation and definition of objectives; (ii) diagnosing students' health and well-being in SS (case study); (iii) initial design and construction of health promotion indicators; (iv) validation based on expert judgement and (v) validation by means of a pilot test. The final construction of the self-assessment tool included 5 areas (healthy habits, affectivity and socialization, emotional well-being, safety and risks, and specific health situations), 9 objectives and 18 indicators deployed through a rubric. Each indicator is discussed in depth, specifying the most appropriate resources and health promotion activities for its application. The final self-assessment tool is designed to be sensitive to and effective for self-assessment of health promotion in SS. It contributes to improving adolescent health on an individual basis and also has an impact on the school environment. Finally, it also promotes analysis of the health content on the curriculum and the teaching-learning method(s) employed at the school. The self-assessment tool has been published open access and its implementation will continue to increase health promotion in SS in Catalonia.

The Combined Use of Gold Nanoparticles and Infrared Radiation Enables Cytosolic Protein Delivery.

Cytosolic protein delivery remains elusive. The inability of most proteins to cross the cellular membrane is a huge hurdle. Here we explore the unique photothermal properties of gold nanorods (AuNRs) to trigger cytosolic delivery of proteins. Both partners, protein and AuNRs, are modified with a protease-resistant cell-penetrating peptide with nuclear targeting properties to induce internalization. Once internalized, spatiotemporal control of protein release is achieved by near-infrared laser irradiation in the safe second biological window. Importantly, catalytic amounts of AuNRs are sufficient to trigger cytosolic protein delivery. To the best of our knowledge, this is the first time that AuNRs with their maximum of absorption in the second biological window are used to deliver proteins into the intracellular space. This strategy represents a powerful tool for the cytosolic delivery of virtually any class of protein.

Self-Sensing Enzyme-Powered Micromotors Equipped with pH-Responsive DNA Nanoswitches.

Biocatalytic micro- and nanomotors have emerged as a new class of active matter self-propelled through enzymatic reactions. The incorporation of functional nanotools could enable the rational design of multifunctional micromotors for simultaneous real-time monitoring of their environment and activity. Herein, we report the combination of DNA nanotechnology and urease-powered micromotors as multifunctional tools able to swim, simultaneously sense the pH of their surrounding environment, and monitor their intrinsic activity. With this purpose, a FRET-labeled triplex DNA nanoswitch for pH sensing was immobilized onto the surface of mesoporous silica-based micromotors. During self-propulsion, urea decomposition and the subsequent release of ammonia led to a fast pH increase, which was detected by real-time monitoring of the FRET efficiency through confocal laser scanning microscopy at different time points (i.e., 30 s, 2 and 10 min). Furthermore, the analysis of speed, enzymatic activity, and propulsive force displayed a similar exponential decay, matching the trend observed for the FRET efficiency. These results illustrate the potential of using specific DNA nanoswitches not only for sensing the micromotors' surrounding microenvironment but also as an indicator of the micromotor activity status, which may aid to the understanding of their performance in different media and in different applications.

Correlation between PSA kinetics and PSMA-PET in prostate cancer restaging: A meta-analysis.

BACKGROUND: Serum prostate-specific antigen (PSA) may predict the risk of positive positron emission tomography/computed tomography with radiolabelled prostate-specific membrane antigen (PSMA-PET/CT) in patients with biochemical recurrent prostate cancer (BRPCa). However, to date, there are no clear data regarding the correlation between PSA kinetics and PSMA-PET findings. We performed a systematic review and meta-analysis to provide evidence-based data in this setting. METHODS: A comprehensive literature search of studies published through October 2018 in PubMed/MEDLINE, EMBASE and Cochrane library databases was performed. A meta-analysis to establish the detection rate (DR) of PSMA-PET using different cut-off values of PSA doubling time (PSAdt) and a pooled analysis to establish whether shorter PSAdt may predict positive PSMA-PET results was performed in patients with BRPCa. RESULTS: Twelve articles were included in the systematic review, and eight articles (including about 1400 patients) were selected for the meta-analysis. The pooled DR including 95% confidence intervals (95%CI) of PSMA-PET in restaging prostate cancer (PCa) patients was 72% (95%CI:60%-82%), increasing to 83% (95%CI:75%-90%) when PSAdt was ≤6 months and decreasing to 60% (95%CI:37%-80%) when PSAdt was >6 months, without a statistical significant difference. PSAdt ≤6 months may predict the positive result of PSMA-PET (pooled odds ratio: 3.22; 95%CI:1.17-8.88). Statistical heterogeneity among the included studies was found. CONCLUSIONS: PSA kinetics, and in particular shorter PSAdt, may be predictor of PSMA-PET positivity in patients with BRPCa. Further larger studies in this setting are warranted.

Advisory groups of children in research on gender-based violence.

Involving children in research is not only advisable but mandatory from both a child rights and an academic perspective. Indeed, recent research has shown that children's participation enriches knowledge and contributes to an in-depth understanding of complex issues, even in sensitive questions such as gender-based violence, leading to improved policy and practice interventions. This article analyses the participation of children both as experts and informants in a research project aimed at creating an early detection model of gender violence applicable in schools. The aims of the study are as follows: i) to analyse the participation strategies used in the research conducted with children in the field of gender-based violence from an ethical and methodological point of view, focusing on strengths and weaknesses, and to identify improvements to be implemented; ii) to collect the experiences of children in this regard. Six expert groups were created specifically for this research project in different locations around Catalonia (Spain). A total of 45 children aged 10-16 participated in all stages of the research, including instrument design (children's questionnaire), discussion of results, building outcomes (model) and dissemination activities (final conference). The questionnaire was answered by a representative sample of 3664 schoolchildren attending 106 schools in Catalonia. This article discusses methodological questions, analysing the benefits and obstacles encountered in working with children, including power relationships, children's voices, engagement, protection, recognitions of capacities and remuneration.

Rac1 and calmodulin interactions modulate dynamics of ARF6-dependent endocytosis.

The main cellular Ca(2+) sensor, calmodulin (CaM), interacts with and regulates several small GTPases, including Rac1. The present study revealed high binding affinity of Rac1 for CaM and uncovered two new essential binding domains in Rac1: the polybasic region, important for phosphatidylinositol-4-phosphate 5-kinase (PIP5K) interaction, and the adjacent prenyl group. CaM inhibition increased Rac1 binding to PIP5K and induced an extensive phosphatidylinositol 4,5-bisphosphate (PI4,5P(2) )-positive tubular membrane network. Immunofluorescence demonstrated that the tubules were plasma membrane invaginations resulting from an ADP-ribosylation factor 6 (ARF6)-dependent and clathrin-independent pathway. The role of Rac1 in this endocytic route was analyzed by expressing constitutively active and inactive mutants. While active Rac1 impaired tubulation, the inactive mutant enhanced it. Intriguingly, inactive mutant expression elicited tubulation by recruiting PIP5K and inhibiting Rac1 at the plasma membrane. Accordingly, CaM inhibition inactivated Rac1 and increased Rac1/PIP5K interaction. Therefore, our findings highlight an important new role for Rac1 and CaM in controlling clathrin-independent endocytosis.

What do children say about seeking help in situations of gender-based violence? Different perspectives depending on whether they have experienced such situations or not.

BACKGROUND: As highlighted in recent studies, children could have a relevant role to play in seeking help in cases of gender-based violence at home, contributing to early detection and empowering them as rights holders and masters of their own lives. Notwithstanding, multiple obstacles to them doing so have been detected. OBJECTIVE: To find out expectations of help among children, seeking the differences between those who have experienced gender-based violence at home and those who have not, by gender and age. PARTICIPANTS AND SETTING: 3664 schoolchildren from 8 to 18 years old (Meanage = 13.16, girls = 50.7 %, secondary school = 64.6 %, primary school = 35.4 %) in Catalonia (Spain). METHODS: Quantitative study. Children responded to an on-line questionnaire. Bivariate analysis and binary multiple logistic regression were used. RESULTS: Children would like to take an active role in seeking help, but were afraid of the consequences and did not know how, or who to ask. Older children and those who had experienced gender-based violence at home were less likely to ask for help (ß = -0.66, [-0.99 - -0.34], p < .001 and ß = -0.67, [-1.04 - -0.27], p < .001, respectively), and were less trusting of adults. CONCLUSIONS: In seeking help, children demand safe services, with clearly identifiable helpers available, able to protect them and their family. Training adults they can trust such as teachers is key. Educating children about what gender-based violence is and where they can seek help is also important.

Targeted immunotherapy against distinct cancer-associated fibroblasts overcomes treatment resistance in refractory HER2+ breast tumors.

About 50% of human epidermal growth factor receptor 2 (HER2)+ breast cancer patients do not benefit from HER2-targeted therapy and almost 20% of them relapse after treatment. Here, we conduct a detailed analysis of two independent cohorts of HER2+ breast cancer patients treated with trastuzumab to elucidate the mechanisms of resistance to anti-HER2 monoclonal antibodies. In addition, we develop a fully humanized immunocompetent model of HER2+ breast cancer recapitulating ex vivo the biological processes that associate with patients' response to treatment. Thanks to these two approaches, we uncover a population of TGF-beta-activated cancer-associated fibroblasts (CAF) specific from tumors resistant to therapy. The presence of this cellular subset related to previously described myofibroblastic (CAF-S1) and podoplanin+ CAF subtypes in breast cancer associates with low IL2 activity. Correspondingly, we find that stroma-targeted stimulation of IL2 pathway in unresponsive tumors restores trastuzumab anti-cancer efficiency. Overall, our study underscores the therapeutic potential of exploiting the tumor microenvironment to identify and overcome mechanisms of resistance to anti-cancer treatment.

AutoScanJ: A Suite of ImageJ Scripts for Intelligent Microscopy.

We developed AutoscanJ, a suite of ImageJ scripts enabling to image targets of interest by automatically driving a motorized microscope at the corresponding locations. For live samples, our software can sequentially detect biological events from their onset and further image them at high resolution, an action that would be impractical by user operation. For fixed samples, the software can dramatically reduce the amount of data acquired and the acquisition duration in situations where statistically few targets of interest are observed per field of view. AutoScanJ is compatible with motorized fluorescence microscopes controlled by Leica LAS AF/X or Micro-Manager. The software is straightforward to set up and new custom image analysis workflows to detect targets of interest can be simply implemented and shared with minimal efforts as independent ImageJ macro functions. We illustrate five different application scenarios with the system ranging from samples fixed on micropatterned surfaces to live cells undergoing several rounds of division. The target detection functions for these applications are provided and can be used as a starting point and a source of inspiration for new applications. Overall, AutoScanJ helps to optimize microscope usage by autonomous operation, and it opens up new experimental avenues by enabling the real-time detection and selective imaging of transient events in live microscopy.

Swiss experience of atezolizumab for platinum-pretreated urinary tract carcinoma: the SAUL study in real-world practice.

AIMS OF THE STUDY: Atezolizumab is an approved therapy for urothelial carcinoma based on results from the IMvigor 210 and IMvigor211 phase II and III trials. The global SAUL study evaluated atezolizumab in a broader patient population more representative of real-world populations. Among approximately 1000 patients treated in SAUL, 25 were treated in Swiss oncology centres. We evaluated outcomes in these patients to provide a better understanding of atezolizumab treatment for urinary tract carcinoma in Swiss clinical practice. METHODS: Eligible patients had locally advanced or metastatic urothelial or non-urothelial urinary tract carcinoma that had progressed during or after one to three prior therapies for inoperable, locally advanced or metastatic disease. Patient populations typically excluded from clinical trials (e.g., patients with renal impairment, treated central nervous system [CNS] metastases, stable controlled autoimmune disease or Eastern Cooperative Oncology Group performance status 2) were also eligible. All patients received atezolizumab 1200 mg every 3 weeks until loss of clinical benefit or unacceptable toxicity. The primary endpoint was safety. Secondary endpoints included overall survival (OS), overall response rate (ORR) and disease control rate (DCR). RESULTS: All 25 Swiss patients had previously received a gemcitabine/platinum doublet. Disease had progressed within 12 months of platinum-based therapy in all but one patient, and 19 (76%) had received one prior line of therapy for metastatic disease. The median duration of atezolizumab therapy was six cycles (range 1–27) corresponding to 3.6 months. Five patients (20%) had received >20 cycles and four (16%) remained on treatment at the data cut-off. Grade 3 adverse events (AEs) occurred in 13 patients (52%) and were considered to be treatment-related in four patients (16%; liver enzyme increases, musculoskeletal pain, diverticulitis and autoimmune hepatitis). There was one grade 4 AE (hypercalcaemia) and no grade 5 AEs. After median follow-up of 17.3 months, median OS was 7.9 months (95% confidence interval [CI] 5.3–not evaluable), the 1-year OS rate was 47% (95% CI 27–65%), the ORR was 12% (95% CI 3–31%) and the DCR was 40% (95% CI 21–61%). Durable clinical benefit (>1 year on treatment) was observed in seven patients (28%), including one with CNS metastases and one with small-cell carcinoma. CONCLUSIONS: Atezolizumab is an active treatment option for platinum-pretreated urinary tract carcinoma, including patients with conditions that typically exclude them from clinical trials. (Trial registration no.: NCT02928406).

Calmodulin modulates H-Ras mediated Raf-1 activation.

We have previously demonstrated that, in COS-1 cells, inhibition of calmodulin increases Ras-GTP levels although it decreases Raf-1 activity and consequently MAPK. The present study analyzes the role of calmodulin in the regulation of Raf-1. First we show, using FRET microscopy, that inhibition of Raf-1 was not a consequence of a decreased interaction between H-Ras and Raf-1. Besides, the analysis of the phosphorylation state of Raf-1 showed that calmodulin, through downstream PI3K, is essential to ensure the Ser338-Raf-1 phosphorylation, critical for Raf-1 activation. We also show that the expression of a dominant negative mutant of PI3K impairs the calmodulin-mediated Raf-1 activation; in addition, both calmodulin and PI3K inhibitors decrease phospho-Ser338 and Raf-1 activity from upstream active H-Ras (H-RasG12V) and this effect is dependent on endocytosis. Importantly, in H-Ras depleted COS-1 cells, calmodulin does not modulate MAPK activation. Altogether, the results suggest that calmodulin regulation of MAPK in COS-1 cells relies upon H-Ras control of Raf-1 activity and involves PI3K.

Autophagy-induced senescence is regulated by p38α signaling.

Apoptosis and senescence are two mutually exclusive cell fate programs that can be activated by stress. The factors that instruct cells to enter into senescence or apoptosis are not fully understood, but both programs can be regulated by the stress kinase p38α. Using an inducible system that specifically activates this pathway, we show that sustained p38α activation suffices to trigger massive autophagosome formation and to enhance the basal autophagic flux. This requires the concurrent effect of increased mitochondrial reactive oxygen species production and the phosphorylation of the ULK1 kinase on Ser-555 by p38α. Moreover, we demonstrate that macroautophagy induction by p38α signaling determines that cancer cells preferentially enter senescence instead of undergoing apoptosis. In agreement with these results, we present evidence that the induction of autophagy by p38α protects cancer cells from chemotherapy-induced apoptosis by promoting senescence. Our results identify a new mechanism of p38α-regulated basal autophagy that controls the fate of cancer cells in response to stress.

Protein kinaseCdelta-calmodulin crosstalk regulates epidermal growth factor receptor exit from early endosomes.

We have recently shown that calmodulin antagonist W13 interferes with the trafficking of the epidermal growth factor receptor (EGFR) and regulates the mitogen-activated protein kinase (MAPK) signaling pathway. In the present study, we demonstrate that in cells in which calmodulin is inhibited, protein kinase C (PKC) inhibitors rapidly restore EGFR and transferrin trafficking through the recycling compartment, although onward transport to the degradative pathway remains arrested. Analysis of PKC isoforms reveals that inhibition of PKCdelta with rottlerin or its down-modulation by using small interfering RNA is specifically responsible for the release of the W13 blockage of EGFR trafficking from early endosomes. The use of the inhibitor Gö 6976, specific for conventional PKCs (alpha, beta, and gamma), or expression of dominant-negative forms of PKClambda, zeta, or epsilon did not restore the effects of W13. Furthermore, in cells treated with W13 and rottlerin, we observed a recovery of brefeldin A tubulation, as well as transport of dextran-fluorescein isothiocyanate toward the late endocytic compartment. These results demonstrate a specific interplay between calmodulin and PKCdelta in the regulation of the morphology of and trafficking from the early endocytic compartment.

Phase I clinical and pharmacological evaluation of the multi-tyrosine kinase inhibitor SU006668 by chronic oral dosing.

SU006668, an oral inhibitor of vascular endothelial growth factor receptor (VEGFR), platelet-derived growth factor receptor (PDGFR) and fibroblast growth factor receptor (FGFR), was administered in fed conditions to 24 patients with advanced solid cancer at 100, 200 and 300 mg/m(2) b.i.d. Dose escalation was discontinued because the maximum tolerated dose was defined at 400 mg/m(2) b.i.d in a concomitant trial. The drug was generally well tolerated although two patients presented possibly drug-related dose-limiting toxicities (pericardial effusion and thrombocytopenia). SU006668 had a non-linear pharmacokinetic profile characterized by AUC and Cmax decreasing from day 1 to day 28 in all patients at all tested doses; a lower apparent bioavailability on day 28 compared to day 1; and a significant concomitant increase of the urinary metabolites. These findings are in agreement with the presence of saturable absorption and metabolic induction. The peculiar pharmacokinetics and >99% protein binding discouraged further clinical development of oral SU006668 in humans.

Role of calmodulin in the modulation of the MAPK signalling pathway and the transactivation of epidermal growth factor receptor mediated by PKC.

We have recently shown that calmodulin (CaM) regulates the trafficking of epidermal growth factor receptor (EGFR) as well as the mitogen-activated protein kinase (MAPK) signalling pathway. However, the overall regulation of the MAPK pathway is achieved through a complex interplay of other several upstream effectors including G-proteins, EGF, EGFR, protein kinase C (PKC), phosphatidylinositol-3-kinase and CaM. In order to understand the role of CaM in the PKC-mediated transactivation of EGFR we have analysed the effect of a CaM antagonist, N-(4-aminobutyl)-5-chloro-2-naphthalenesulfonamide, on the 12-O-tetradecanoylphorbol-13-acetate-mediated activation of EGFR and the subsequent MAPK activation. The results show that CaM interferes with MAPK activation and the transactivation of EGFR mediated by PKC.

La evaluación de las políticas municipales de juventud a partir de un sistema de indicadores / Evaluation of municipal youth policies through an indicators system

En este artículo presentamos un sistema de indicadores (SIAPJove) para evaluar políticas municipales de juventud. El sistema ha sido creado y validado por un grupo de individuos expertos y se ha aplicado en tres municipios de Cataluña en el Estado Español, en forma de estudio de caso para comprobar su aplicabilidad y eficacia. El resultado es un instrumento con 12 ámbitos de evaluación, 32 objetivos de evaluación y 83 indicadores. Permite evaluar la situación de dichas políticas, hacer evidentes las tendencias y los cambios, valorar su nivel de eficacia y contribuir a establecer objetivos a corto y medio plazo. Asimismo, se puede utilizar como herramienta para la autoevaluación, para reflexionar sobre la propia acción y aprender de los errores y las dificultades en el desarrollo de las políticas municipales de juventud...

Open-label, phase II, multicenter, randomized study of the efficacy and safety of two dose levels of Pertuzumab, a human epidermal growth factor receptor 2 dimerization inhibitor, in patients with human epidermal growth factor receptor 2-negative metastatic breast cancer.

PURPOSE: Pertuzumab is a humanized monoclonal antibody inhibiting human epidermal growth factor receptor 2 (HER2) dimerization. The aim of this phase II trial was to assess the antitumor activity and safety profile of pertuzumab monotherapy in patients with HER2-negative metastatic breast cancer. The utility of biomarkers detected in paraffin-embedded tissue as predictors of response was also explored. PATIENTS AND METHODS: This was an international, multicenter, open-label, randomized phase II study. Patients (n = 79) with centrally confirmed HER2-negative metastatic breast cancer were randomly assigned to receive pertuzumab once every 3 weeks with a loading dose of 840 mg followed thereafter by either 420 mg (arm A) or 1,050 mg (arm B). Patients were stratified by country and prior taxane therapy. RESULTS: Of 79 patients who were randomly assigned, 78 were included in the intent-to-treat population. In arm A (n = 41), two patients had partial responses, and 18 patients (44%) experienced stable disease (SD) lasting > or = 12 weeks. In arm B (n = 37), SD was observed in 14 patients (38%). Overall, six of 78 patients responded or had SD > or = 6 months. Pertuzumab was generally well tolerated, and most adverse events were mild to moderate. Decline in left ventricular ejection fraction of > or = 10% and/or to less than 50% was observed in eight patients, with one case of congestive heart failure in arm A. Pharmacokinetic data supported a fixed dose of pertuzumab once every 3 weeks. CONCLUSION: The limited efficacy observed in this study, generally SD of relatively short duration, suggested little benefit of further investigation of single-agent pertuzumab in unselected patients with HER2-negative disease.

Juventud, políticas públicas y crisis en España: triángulo mágico o triángulo de las Bermudas? / Youth, public policies and crisis in Spain: magic triangle or Bermuda Triangle? / Juventude, políticas públicas e crise na Espanha: Triângulo mágico ou Triângulo das Bermudas?

En tiempos de crisis, las políticas de juventud están experimentando enormes recortes y transformaciones hasta el punto que hemos llegado a preguntarnos si realmente existen como políticas públicas con entidad propia. La situación en la que se encuentran muchos sujetos jóvenes en España les lleva a preguntarse dónde están las redes de protección tradicionales: la familia, las ONG’s o el Estado de Bienestar, cuando realmente se los necesita. Nuestro objetivo en este artículo es presentar y discutir la situación de las políticas de juventud en España en el contexto actual de austeridad y drásticos recortes sociales. Este análisis lo llevamos a cabo a partir de los parámetros del triángulo mágico que unen las políticas, la investigación y el trabajo social con jóvenes.

In times of crisis, the youth policies are experiencing enormous cutbacks and transformations to the point that we are wondering whether they really exist as public policies with their own entity. The situation in which many young people find themselves in Spain leads them to wonder where the traditional protection networks are: The family, the NGO’s or the Welfare State, when they are really needed. Our objective in this article is to show and discuss the situation of the youth policies in Spain in the present context of social austerity and drastic cutbacks. We carry out this analysis from the parameters of the magical triangle that unite policies, research and social work with young people.

Em tempos de crise, as políticas de juventude estão enfrentando enormes cortes e transformações ao ponto de nos perguntarmos se as políticas públicas existem realmente com entidade própria. A situação em que se encontram muitos jovens na Espanha faz que eles agora se perguntem onde estão as redes tradicionais de segurança: a família, as ONGs ou o estado do bemestar, quando você realmente precisa delas. O objetivo deste artigo é apresentar e discutir a situação na Espanha, em relação às políticas públicas para a juventude no contexto atual de austeridade e de cortes drásticos de bem-estar. Analisamos a situação dos jovens e das politicas de juventude na Espanha, através dos parâmetros do triângulo mágico ligando política, pesquisa e trabalho social com jovens.

Protein kinase Cdelta and calmodulin regulate epidermal growth factor receptor recycling from early endosomes through Arp2/3 complex and cortactin.

The intracellular trafficking of the epidermal growth factor receptor (EGFR) is regulated by a cross-talk between calmodulin (CaM) and protein kinase Cdelta (PKCdelta). On inhibition of CaM, PKCdelta promotes the formation of enlarged early endosomes and blocks EGFR recycling and degradation. Here, we show that PKCdelta impairs EGFR trafficking due to the formation of an F-actin coat surrounding early endosomes. The PKCdelta-induced polymerization of actin is orchestrated by the Arp2/3 complex and requires the interaction of cortactin with PKCdelta. Accordingly, inhibition of actin polymerization by using cytochalasin D or by overexpression of active cofilin, restored the normal morphology of the organelle and the recycling of EGFR. Similar results were obtained after down-regulation of cortactin and the sequestration of the Arp2/3 complex. Furthermore we demonstrate an interaction of cortactin with CaM and PKCdelta, the latter being dependent on CaM inhibition. In summary, this study provides the first evidence that CaM and PKCdelta organize actin dynamics in the early endosomal compartment, thereby regulating the intracellular trafficking of EGFR.