Cortactin Expression in Hematopoietic Cells

Alcohol-sourced acetate impairs T cell function by promoting cortactin acetylation

Alcohol is among the most widely consumed dietary substances. Excessive alcohol consumption damages the liver, heart, and brain. Alcohol also has strong immunoregulatory properties. Here, we report how alcohol impairs T cell function via acetylation of cortactin, a protein that binds filamentous actin and facilitates branching. Upon alcohol consumption, acetate, the metabolite of alcohol, accumulates in lymphoid organs. T cells exposed to acetate, exhibit increased acetylation of cortactin. Acetylation of cortactin inhibits filamentous actin binding and hence reduces T cell migration, immune synapse formation and activation. While mutated, acetylation-resistant cortactin rescues the acetate-induced inhibition of T cell migration, primary mouse cortactin knockout T cells exhibited impaired migration. Acetate-induced cytoskeletal changes effectively inhibited activation, proliferation, and immune synapse formation in T cells in vitro and in vivo in an influenza infection model in mice. Together these findings reveal cortactin as a possible target for mitigation of T cell driven autoimmune diseases.

T cell functions and organ infiltration by leukemic T cells require cortactin

T cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that is still fatal in many cases. T cell blasts are characterized by hyperactivation and strong proliferative and migratory capacities. The chemokine receptor CXCR4 is involved in mediating malignant T cell properties, and cortactin has been shown to control CXCR4 surface localization in T-ALL cells. We have previously shown that cortactin overexpression is correlated with organ infiltration and relapse in B-ALL. However, the role of cortactin in T cell biology and T-ALL remains elusive. Here, we analyzed the functional relevance of cortactin for T cell activation and migration and the implications for T-ALL development. We found that cortactin is upregulated in response to T cell receptor engagement and recruited to the immune synapse in normal T cells. Loss of cortactin caused reduced IL-2 production and proliferation. Cortactin-depleted T cells showed defects in immune synapse formation and migrated less due to impaired actin polymerization in response to T cell receptor and CXCR4 stimulation. Leukemic T cells expressed much higher levels of cortactin compared to normal T cells that correlated with greater migratory capacity. Xenotransplantation assays in NSG mice revealed that cortactin-depleted human leukemic T cells colonized the bone marrow significantly less and failed to infiltrate the central nervous system, suggesting that cortactin overexpression drives organ infiltration, which is a major complication of T-ALL relapse. Thus, cortactin could serve as a potential therapeutic target for T-ALL and other pathologies involving aberrant T cell responses.

Cortactin Expression is a Novel Biomarker for Risk Stratification of T-Cell Acute Lymphoblastic Leukemia

The role of cortactin in T-cell acute lymphoblastic leukemia (T-ALL) tissue infiltration has been previously reported. However, its impact on patients' responsiveness to therapy and patient's outcome was not previously addressed. This study was conducted on 60 T-ALL pediatric patients at diagnosis and 10 nonleukemic controls. Cortactin and HS1 expressions were identified by real-time polymerase chain reaction. Cortactin and HS1 expression were significantly higher in T-All patients as compared with controls as well as postinduction levels (P≤0.001 for both). The high cortactin expression was significantly associated with high peripheral white cell counts (P≤0.001), blood blast cells (P≤0.001) and central nervous system (CNS) infiltration (P≤0.001), and early precursor T-ALL subtype (P≤0.001) as compared with the remaining groups. The induction of remission response was significantly higher in T-ALL patients with lower cortactin expression levels as compared with T-ALL patients with higher one (P≤0.001). The high cortactin and HS1 expressions were significantly predictors of CNS infiltrations (hazard ratios [HR]: 1.051, confidence interval [CI]: 1.02-1.13, P=0.04 and HR: 1.87, CI: 1.23-2.091, P=0.002, respectively) and bone marrow relapse (HR: 1.43, CI: 1.18-1.92, P=0.004 and HR: 1.07, CI: 1.01-1.24, P=0.002, respectively). Furthermore, high cortactin expression levels were associated with shorter B-ALL patients' overall survival as compared with those with lower cortactin levels (P=0.002). In conclusion, high expression of cortactin and/or HS1 at diagnosis is a bad prognostic marker of T-ALL patients' outcome. Moreover, cortactin and/or HS1 expression could be used as a biomarker for refining risk stratification of T-ALL.

The Helicobacter pylori type IV secretion system upregulates epithelial cortactin expression by a CagA- and JNK-dependent pathway

Cortactin represents an important actin-binding factor, which controls actin-cytoskeletal remodelling in host cells. In this way, cortactin has been shown to exhibit crucial functions both for cell movement and tumour cell invasion. In addition, the cortactin gene cttn is amplified in various cancer types of humans. Helicobacter pylori is the causative agent of multiple gastric diseases and represents a significant risk factor for the development of gastric adenocarcinoma. It has been repeatedly shown that H. pylori manipulates cancer-related signal transduction events in infected gastric epithelial cells such as the phosphorylation status of cortactin. In fact, H. pylori modifies the activity of cortactin's binding partners to stimulate changes in the actin-cytoskeleton, cell adhesion and motility. Here we show that H. pylori infection of cultured AGS and Caco-2 cells for 24-48 hr leads to the overexpression of cortactin by 2-3 fold at the protein level. We demonstrate that this activity requires the integrity of the type IV secretion system (T4SS) encoded by the cag pathogenicity island (cagPAI) as well as the translocated effector protein CagA. We further show that ectopic expression of CagA is sufficient to stimulate cortactin overexpression. Furthermore, phosphorylation of CagA at the EPIYA-repeat region is not required, suggesting that this CagA activity proceeds in a phosphorylation-independent fashion. Inhibitor studies further demonstrate that the involved signalling pathway comprises the mitogen-activated protein kinase JNK (c-Jun N-terminal kinase), but not ERK1/2 or p38. Taken together, using H. pylori as a model system, this study discovered a previously unrecognised cortactin activation cascade by a microbial pathogen. We suggest that H. pylori targets cortactin to manipulate the cellular architecture and epithelial barrier functions that can impact gastric cancer development. TAKE AWAYS: Helicobacter pylori infection induces overexpression of cortactin at the protein level Cortactin upregulation requires the T4SS and effector protein CagA Ectopic expression of CagA is sufficient to stimulate cortactin overexpression Overexpression of cortactin proceeds CagA phosphorylation-independent The involved host cell signalling pathway comprises the MAP kinase JNK.