Abstract
The combination of hydrodynamic and electrophoretic experiments and computer simulations is a powerful approach to study the interaction between proteins. In this work, we present hydrodynamic and electrophoretic experiments in an aqueous solution along with molecular dynamics and hydrodynamic modeling to monitor and compute biophysical properties of the interactions between the extracellular domain of the HER2 protein (eHER2) and the monoclonal antibody trastuzumab (TZM). The importance of this system relies on the fact that the overexpression of HER2 protein is related with the poor prognosis breast cancers (HER2++ positives), while the TZM is a monoclonal antibody for the treatment of this cancer. We have found and characterized two different complexes between the TZM and eHER2 proteins (1:1 and 1:2 TZM:eHER2 complexes). The conformational features of these complexes regulate their hydrodynamic and electrostatic properties. Thus, the results indicate a high degree of molecular flexibility in the systems that ultimately leads to higher values of the intrinsic viscosity, as well as lower values of diffusion coefficient than those expected for simple globular proteins. A highly asymmetric charge distribution is detected for the monovalent complex (1:1 complex), which has strong implications in correlations between the experimental electrophoretic mobility and the modeled net charge. In order to understand the dynamics of these systems and the role of the specific domains involved, it is essential to find biophysical correlations between dynamics, macroscopic transport and electrostatic properties. The results should be of general interest for researchers working in this area.
Highlights
HER2, one of the epidermal growth factor receptors family (EGFR), is well-known to be overexpressed in aggressive human breast cancer
The importance of this system relies on the fact that the overexpression of HER2 protein is related with the poor prognosis breast cancers (HER2++ positives), while the TZM is a monoclonal antibody for the treatment of this cancer
The result obtained for TZM are in contrast wit9hofth18e high negative charge density of the g-extracellular domain of the HER2 protein (eHER2) surface, as judged by the results shown in Table 2, apgrreeseummeanbtlbyedtwueetno tehxepcoosmedpuastaptaiortnicalahnyddgroludtyanmaimc iaccaidnsalryessiisdoubetsa.iCnehdanfrgoems itnheeiMthDertrthajeecstiogrnieosratnhde tmheagenxpiteurdime oenf tahlemζ-epaosuternetmiaelnotfs tfhoerstehesyssytsetmems csaunnsdeerrvsetuasdya. qTuhaeliptaetricveenitnagdeicdatiifofenreonfccehbaentgweeseinn tthhee csaulrcfualcaetecdharngdeedxepnesriitmy,een.tga.l, vspaeluceifsicarinetleersascthioanns5b%et,wweitehntthheeebxicoemptaicornomofotlheecudliefsfu[s5i2o]n
Summary
HER2 (or ErbB2), one of the epidermal growth factor receptors family (EGFR), is well-known to be overexpressed in aggressive human breast cancer. High amount of HER2 on the cell surface promotes the dimer formation with HER2 (homodimers) or other member of the EFGRs family (heterodimers). These dimers lead to the phosphorylation of the intracellular tyrosine kinase domains, which trigger several signaling pathways related to cellular oncogenic processes (i.e., cellular proliferation, survival, motility, or angiogenesis) [1]. Several mechanisms of action of TZM have been proposed: (i) induction of antibody-dependent cellular cytotoxicity, (ii) prevention of e-HER2 domain cleavage and the most important in HER-2 overexpressed cancers, (iii) the dimerization inhibition which prevents the cell growth and proliferation [8]. Irrespective of the precise mechanism involved, the overall result is two-fold: an increase of the apoptosis and a suppression of the cell proliferation
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