Interactions Between Fullerene Nanocrystals And Camkii Protein In Brain And Heart Tissues

Nanoparticle-protein interactions hold one of the keys for understanding the diverse and oftentimes unexpected biological effects elicited by engineered nanomaterials. In a biological environment, nanoparticles may encounter and interact with thousands of proteins. Some of these interactions may be transient, with proteins on a come-and-go basis, while others are stable, with proteins getting "adsorbed" and forming a protein conora on the surface of nanoparticles.As the the biological identity of nanoparticles, the protein coronas are likely to exert an influence on the biological effects of nanoparticles. Indeed, many interactions between nanoparticles and proteins are oftentimes perceived as non-specific protein adsorption, with protein unfolding and deactivation as the most likely consequences, but in almost all of the cases where the binding mechanism has been determined, sequence-specific and conformationally-driven interactions were uncovered.There are thousands of cellular signaling proteins and millions of protein-protein interactions found in cells. In these processes, signals for driving critically-important cell decisions such as growth or differentiation are oftentimes transmitted through the highly specific interaction between two protein molecules, causing changes in the functionality for one or both of the proteins, such as the protein’s enzymatic activity, intracellular location, or association with other signaling proteins. However the potential of a nanoparticle-protein interaction to mimic a protein-protein interaction in a cellular signaling process, characterized by stringent binding specificity and robust structural and functional modulation for the interacting protein, has not been adequately demonstrated.Buckminster fullerene C60is a classic engineered nanomaterial with a remarkable geometrical structure and unique physicochemical properties. Nowadays, C60and its derivatives are widely used in the field of biomedicine for their outstanding biological activities. Some of these biological effects are likely manifested through C60interaction with the key proteins involved in the underlying biological processes. However, direct proof for interaction-resulted functional modulation has been obtained for only a few of the proteins. In this thesis, we proposed several important insights regarding nanoparticle-protein interactions in a cellular environment.In part I, we revealed a stable high-affinity interaction between the Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKIα), a multimeric intracellular serine/threonine kinase central to Ca2+signal transduction and critical for learning and memory, with the water-suspended C60nanocrystals (Nano C60). This highly specific interaction, dictated by a set of amino acids (D246/K250) within the catalytic domain of the CaMKIIa subunit, is reminiscent of the well-documented interaction between CaMKIIa and the NMDA receptor subunit NR2B, a neuronal membrane protein that also binds to the catalytic domain of CaMKIIα, leading to the similar functional consequences, including generation of autonomous CaMKIIa activity in the absence of T286autophosphorylation, calmodulin (CaM) trapping and translocation to post-synaptic sites for CaMKIIα. We further demonstrated that binding to Nano C60locks CaMKIIa in an active conformation by preventing the re-association of the autbinhibitory sequence with the catalytic domain after Ca2+withdrawal. Our results provide a compelling example that an inorganic nanoparticle has the capacity to act like a cellular signaling protein in exerting robust structural and functional modulation for an interacting protein. Meanwhile, the ability of Nano C60to sustain the Ca2+/CaM-autonomous CaMKIIa activity we revealed might provide a beneficial effect on learning and memory, thus opening up the possibility for the therapeutic intervention of neural degeneration diseases.In part II, we showed the biological effects of fullerene C60nanoparticles on CaMKIIδ in heart tissue.We found the ability of fullerene C60nanoparticles to induce oxidation of CaMKIIδ, sustain its activity in the absence of Ca2+/CaM, and increase the level of T286auto-phosphorylation, which leads to cardiac injury and apoptosis in cardiomyocytes. These researches may provide a theoretical basis for both the bio-safety and the potential therapeutic applications of fullerene C60.