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Aberrations of the epidermal growth factor receptor (EGFR), for example, mutations and overexpression, play pivotal roles in various cellular functions, such as proliferation, migration, and cell differentiation. Approved small molecule-based inhibitors, including gefitinib and erlotinib, are used clinically to target the tyrosine kinase domain of EGFR (TK-EGFR). However, the severity of the side effects, off-target effects, and drug resistance is a concern. Cyclic peptides are a well-known peptide format with high stability and are promising molecules for drug development. Herein, the Ph.D.™-C7C phage display library was used to screen cyclic peptides against TK-EGFR. Biopanning, both with and without propagation methods, was performed to assess the highest capacity peptides using the enzymatic activity of TK-EGFR. Interestingly, NP1, a peptide selected during biopanning without propagation demonstrated an inhibitory effect against TK-EGFR at IC50 within the nanomolar range; this effect was better than that of P1 obtained using biopanning with propagation. Moreover, NP1 elicited EGFR with an affinity binding (KD ) value of 18.40 ± 5.50 µM by surface plasmon resonance (SPR). Introducing cell-penetrating peptides or Arginine-9 (Arg9) at the N-terminus of NP1 thus improves cell-penetrability and can lead to the inhibition of EGFR-driven cancer cell lines; however, it exhibits no hepatotoxicity. Furthermore, NP1 caused a decrease in phosphorylated EGFR after activation within cells. A docking model shows that NP1 interacted primarily with TK-EGFR via hydrogen bonding. Together, this suggests that NP1 is a novel EGFR peptide inhibitor candidate with specificity and selectivity toward TK-EGFR, and may be applied to targeted therapy.

The family of human epidermal growth factor receptors (HER) is involved in tumor cell growth. Homodimerization and heterodimerization of the HER family are important for activation of these receptors. The structures of homodimer conformation are well characterized, while the structures of heterodimer conformations, especially between HER1 and HER2, are not completely understood. In this study, two models of possible asymmetric HER1/HER2 kinase domains were built. Molecular dynamics simulations and molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) methods were applied to examine the possibility of these two-heterodimer interactions. From our results, it could be concluded that the HER2 kinase domain prefers to serve as the receiver rather than the activator. Key binding residues of this dimer complex at N lobe of HER2 is ALA683 and at C lobe of HER1 are GLU914, GLU917, and ASP930. This study will be useful in allowing us to predict and be able to control activity of this enzyme in disease in the future. Graphical abstract A model of the asymmetric dimer of HER1-HER2 heterodimer with key intereaction residues in (a) HER1A and (b) HER2R by molecular dynamic simulation.

The role of six cysteines of Ca(V)3.1 in channel gating was investigated. C241, C271, C282, C298, C313, and C323, located in the extracellular loop between segment IS5 and the pore helix, were each mutated to alanine; the resultant channels were expressed and studied by patch clamping in HEK293 cells. C298A and C313A conducted calcium currents, while the other mutants were not functional. C298A and C313A as well as double mutation C298/313A significantly reduced the amplitude of the calcium currents, shifted the activation curve in the depolarizing direction and slowed down channel inactivation. Redox agents dithiothreitol (DTT) and 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) shifted the current activation curve of wild-type channels in the hyperpolarizing direction. Activation curve for all mutated channels was shifted in hyperpolarizing direction by DTT while DTNB caused a depolarizing shift. Our study reveals that the cysteines we studied have an essential role in Ca(V)3.1 gating. We hypothesize that cysteines in the large extracellular loop of Ca(V)3.1 form bridges within the loop and/or neighboring channel segments that are essential for channel gating.

To test the hypothesis that olfactory receptors (ORs) recognize different molecular features of odor molecules termed "odotypes", we studied receptor-ligand interactions of two human and two mouse ORs, recognizing (-)citronellal. Structurally similar receptors provide identical binding pockets (OLFR43, OR1A1, and OR1A2), and have comparable EC(50) values. Other ORs with lower sequence identity bind (-)citronellal in a different way, leading to different EC(50) values.

Increased cholesterol levels are associated with multiple pathological conditions. In this work, molecular dynamics simulations were applied to observe the influence of membrane cholesterol levels on a voltage-gated sodium channel. Different lipid compositions are modeled around the channel to obtain information about the possible effects by which cholesterol influences NavAb channels. Cholesterol was normally not directly interacting with either the closed or inactivated conformation. Cholesterol increased lipid packing implying that it plays a crucial role in restricting lipid movement in the region around 1 nm of the channel in a 1-palmitoyl-2-oeleoyl phosphatidylcholine matrix. Our results provide the first computational indication of an indirect modulation of NavAb channels by membrane cholesterol.

GABA-A receptors are the major inhibitory transmitter receptors in the brain and the site of action of many clinically important drugs. CGS 9895 and many other pyrazoloquinolinones are high affinity null modulators at the benzodiazepine (Bz) binding site and at higher concentrations also modulate the receptors via the α+β- interface. To gain insights into the interactions of CGS 9895 with both binding sites, we used our homology models to select γ2- side amino acid residues important for Bz binding and to incorporate them into the β3- side by site directed mutagenesis. These mutated β3 subunits were co-expressed with α subunits. The recombinant receptors were investigated by the two electrode voltage clamp method in Xenopus laevis oocytes and by radioligand binding assays. With only four mutations we were able to introduce a high affinity binding site for CGS 9895 into αβ3 receptors. Furthermore, GABA currents of several recombinant αβ3(mut) receptors could be modulated by the tested pyrazoloquinolinones ...