Grb2 controls phosphorylation of FGFR2 by inhibiting receptor kinase and Shp2 phosphatase activity

Inhibition of SHP2 in basal-like and triple-negative breast cells induces basal-to-luminal transition, hormone dependency, and sensitivity to anti-hormone treatment

Background

The Src homology phosphotyrosyl phosphatase 2 (SHP2) is a positive effector of cell growth and survival signaling as well transformation induced by multiple tyrosine kinase oncogenes. Since the basal-like and triple-negative breast cancer (BTBC) is characterized by dysregulation of multiple tyrosine kinase oncogenes, we wanted to determine the importance of SHP2 in BTBC cell lines.

Methods

Short hairpin RNA-based and dominant-negative expression-based SHP2 inhibition techniques were used to interrogate the functional importance of SHP2 in BTBC cell biology. In addition, cell viability and proliferation assays were used to determine hormone dependency for growth and sensitivity to anti-estrogen treatment.

Results

We show that inhibition of SHP2 in BTBC cells induces luminal-like epithelial morphology while suppressing the mesenchymal and invasive property. We have termed this process as basal-to-luminal transition (BLT). The occurrence of BLT was confirmed by the loss of the basal marker alpha smooth muscle actin and the acquisition of the luminal marker cytokeratin 18 (CK18) expression. Furthermore, the occurrence of BLT led to estrogen receptor alpha (ERα) expression, hormone dependency, and sensitivity to tamoxifen treatment.

Conclusions

Our data show that inhibition of SHP2 induces BLT, ERα expression, dependency on estrogen for growth, and sensitivity to anti-hormone therapy. Therefore, inhibition of SHP2 may provide a therapeutic benefit in basal-like and triple-negative breast cancer.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1131-2) contains supplementary material, which is available to authorized users.

Careless talk costs lives: fibroblast growth factor receptor signalling and the consequences of pathway malfunction

Since its discovery 40 years ago, fibroblast growth factor (FGF) receptor (FGFR) signalling has been found to regulate fundamental cellular behaviours in a wide range of cell types. FGFRs regulate development, homeostasis, and repair and are implicated in many disorders and diseases; and indeed, there is extensive potential for severe consequences, be they developmental, homeostatic, or oncogenic, should FGF-FGFR signalling go awry, so careful control of the pathway is critically important. In this review, we discuss the recent developments in the FGF field, highlighting how FGFR signalling works in normal cells, how it can go wrong, how frequently it is compromised, and how it is being targeted therapeutically.

Next generation sequencing reveals regulation of distinct Aedes microRNAs during chikungunya virus development

Background

Application of genomics and Next Generation sequencing has led to the identification of new class of cellular functional molecules, namely, small RNAs. Of the several classes of ncRNAs (non-coding RNA), microRNAs have been demonstrated to exert determinative influence on various cellular processes. It is becoming abundantly clear that host/vector/pathogen encoded microRNAs impact eventual pathogenesis. In this context, the participation of vector based microRNAs in disease transmission and pathogen development is being investigated intensively. A few studies have highlighted the role of vector encoded microRNAs in pathogen infection. We conducted this study to evaluate the role of host miRNAs upon CHIKV (Chikungunya Virus) infection in an important vector, Aedes albopictus.

Findings

We identified 88 and 79 known miRNAs in uninfected and CHIKV infected Ae. albopictus Singh's cell line respectively. We further identified nine novel miRNAs in Ae. albopictus. Comparison of the two libraries revealed differential expression of 77 common miRNAs between them. CHIKV infection specifically altered the miRNA profile of a specific set of eight miRNAs. Putative targets of these regulated miRNAs were identified and classified into their pathways.

Conclusions

In our study we have identified and described the profiles of various miRNAs upon CHIKV infection in Ae. albopictus. This investigation provides an insight about cellular modification by miRNAs during CHIKV infection and the results provide leads for identifying potential candidates for vector based antiviral strategies.

Small, non-coding, RNAs such as microRNAs (miRNA) of length 18–24 nucleotide are reported in wide range of organisms and known to play a determinative role in regulation of various cellular processes. They have also reported to have regulatory roles during pathogen infection, maturation and transmission. Chikungunya virus is an important alphavirus transmitted through two important vectors, Aedes aegypti and Ae. albopictus. While Ae. aegypti has been the preferred vector for transmission of this virus, recently, Ae. albopictus has gained notoriety for disease transmission. Using Illumina platform, we sequenced the small RNA population an Aedes albopictus cell line infected with chikungunya virus. We studied the expression modulation of miRNAs upon CHIKV infection and found distinct set of miRNAs regulated in Aedes upon CHIKV infection. We further predicted the targets of these miRNAs and performed pathway analysis of these targets. The cellular functional targets of some of these miRNAs overlapped suggesting aggressive participation of the targeted pathways in establishing CHIKV infection.

Grb2 promotes integrin-induced focal adhesion kinase (FAK) autophosphorylation and directs the phosphorylation of protein tyrosine phosphatase α by the Src-FAK kinase complex

The integrin-activated Src-focal adhesion kinase (FAK) kinase complex phosphorylates PTPα at Tyr789, initiating PTPα-mediated signaling that promotes cell migration. Recruitment of the BCAR3-Cas complex by PTPα-phospho-Tyr789 at focal adhesions is one mechanism of PTPα signaling. The adaptor protein Grb2 is also recruited by PTPα-phospho-Tyr789, although the role of the PTPα-Grb2 complex in integrin signaling is unknown. We show that silencing Grb2 expression in fibroblasts abolishes PTPα-Tyr789 phosphorylation and that this is due to two unexpected actions of Grb2. First, Grb2 promotes integrin-induced autophosphorylation of FAK-Tyr397. This is impaired in Grb2-depleted cells and prohibits FAK activation and formation of the Src-FAK complex. Grb2-depleted cells contain less paxillin, and paxillin overexpression rescues FAK-Tyr397 phosphorylation, suggesting that the FAK-activating action of Grb2 involves paxillin. A second distinct role for Grb2 in PTPα-Tyr789 phosphorylation involves Grb2-mediated coupling of Src-FAK and PTPα. This requires two phosphosites, FAK-Tyr925 and PTPα-Tyr789, for Grb2-Src homology 2 (SH2) binding. We propose that a Grb2 dimer links FAK and PTPα, and this positions active Src-FAK in proximity with other, perhaps integrin-clustered, molecules of PTPα to enable maximal PTPα-Tyr789 phosphorylation. These findings identify Grb2 as a new FAK activator and reveal its essential role in coordinating PTPα tyrosine phosphorylation to enable downstream integrin signaling and migration.