Thymocytes convert graded T cell receptor (TCR) signals into positive selection or deletion, and activation of extracellular signal-related kinase (ERK), p38, and Jun N-terminal protein kinase (JNK) mitogen-activated protein kinases (MAPKs) has been postulated to play a discriminatory role. Two families of Ras guanine nucleotide exchange factors (RasGEFs), SOS and RasGRP, activate Ras and the d...

The SH2 and SH3 domain structural integrity and functionality were confirmed by peptide binding assays. Binding studies using two phosphotyrosine peptides derived from EGFR (FLPVPE{pY}IN-QSVPKR) and Shc (EEPPDHQ{pY}YNDFPGK) for the Grb2 SH2 domain and a SOS1-derived proline-rich peptide (PVPPPVPPRRRPEY) for the SH3 domains were performed using MST 1. Grb2 was fluorescently labeled using Atto488...

To understand the mechanisms by which electrical activity may generate long-term responses in the nervous system, we examined how activation of voltage-sensitive calcium channels (VSCCs) can stimulate the Ras/mitogen-activated protein kinase (MAPK) signaling pathway. Calcium influx through L-type VSCCs leads to tyrosine phosphorylation of the adaptor protein Shc and its association with the ada...

The human airway is lined with respiratory epithelial cells, which create a critical barrier through the formation of apical tight junctions. To investigate the molecular mechanisms underlying this process, an RNAi screen for guanine nucleotide exchange factors (GEFs) was performed in human bronchial epithelial cells (16HBE). We report that SOS1, acting through the Ras/MEK/ERK pathway, is essen...

The precise mechanisms via which Rac1 is activated by cadherin junctions are not fully known. In keratinocytes Rac1 activation by cadherin junctions requires EGFR signalling, but how EGFR does so is unclear. To address which activator could mediate E-cadherin signalling to Rac1, we investigated EGFR and two Rac1 GEFs, SOS1 and DOCK180. EGFR RNAi prevented junction-induced Rac1 activation and le...

Despite its key role in mediating a plethora of cellular signaling cascades pertinent to health and disease, little is known about the structural landscape of the proline-rich (PR) domain of Sos1 guanine nucleotide exchange factor. Herein, using a battery of biophysical tools, we provide evidence that the PR domain of Sos1 is structurally disordered and adopts an extended random coil-like confo...