Investigating the protein-protein Interaction between Aquaporin 4 & Calmodulin

Sammanfattning: Around 60 million people around the world are struggling with a traumatic brain or spinal cord injury. The swelling of the brain or spinal cord happen when the water content in the CNS increase due, infection, tumor growth or brain edema. AQP4 is a membrane water channel which mediates the water flux across the blood brain barrier (BBB) and blood spinal-cord barrier (BSCB). We believe that protein-protein interactions play crucial roles in regulating human Aquaporin’s by gating or trafficking, but the mechanism of how protein-protein interaction mediate water transport across the membrane remain poorly characterized. It has been suggested that AQP4 protein could be regulated by protein calmodulin through complicated and poorly characterized mechanism. It has been suggested that protein AQP4 is regulated by trafficking mechanism, through directly binding of CaM to AQP4. In order to demonstrate this hypothesis, AQP4 was purified from P.pastoris cells and incorporated into nanodiscs. Activated CaM will be added to the nanodisc to study the binding mode between CaM and AQP4. The purified nanodisc, used for further analysis using Cryo-EM technology. By this technique we proved that AQP4 can bind to two calmodulin protein directly.