| Abstract [eng] |
S100 family proteins are involved in different cell activities: proliferation, survival, move- ment, inflammatory signalling and reproduction. Because of the wide range of functions, these proteins can be associated with many diseases, including cancer and neurodegenera- tive disorders. There are reports showing that S100A9 protein can aggregate into amyloid fibrils and is possibly involved in Alzheimer’s and Parkinson’s diseases. Similar to other members in S100 family, S100A9 stability can be regulated by calcium, however there is too little information on how calcium ions affect S100A9 protein stability and even less how S100A9 aggregates into amyloid-like structures. Therefore we decided to investigate these properties. Thermal unfolding of the protein was monitored using ANS fluorescence assay. Calcium- protein binding events were studied using isothermal titration calorimetry (ITC). Agg- regation kinetics of S100A9 were observed using Thioflavin-T (ThT) fluorescence assay. Formed amyloid-like fibrils were observed using atomic force microscopy and the nature of fibrils was confirmed using specific A11 and OC antibodies. Results show, that calcium exponentially increases protein thermal stability and in- hibits the rate of aggregation. ITC data suggests, that calcium binds to multiple sites and induces conformational changes of the protein structure, however more detailed research is needed to identify different protein states. Overall aggregation experiments revealed that S100A9 easily forms amyloid fibrils and can influence Alpha-synuclein aggregation, which is related to Parkinson disease. |
