Macropinocytosis: Taking a sip of the nanoscopic world

Author: Shayne Quinn, Department of Nanoscience & Nanoengineering

Mentor: Dr. Brandon Scott, Department of Nanoscience and Nanoengineering

Mentor: Dr. Robert Anderson, Department of Nanoscience and Nanoengineering

The innate immune system depends on macrophage activities including tissue fluid filtration in search of foreign material, leading the front lines of the immune response, and being recruited as reinforcements to fight off dangerous pathogens and bacteria. Understanding how macrophages interact with their environment is vital for the development of new technologies that can strengthen and stimulate the immune system. Macrophages use a process known as macropinocytosis (also known as cell drinking) to sample their environment by taking in a large gulp of their surroundings to create a vessel known as a ‘macropinosome’. Macropinosomes are formed by dynamic actin-rich membrane ruffles that form a vesicle that is trafficked through the cell to be processed, providing the cell with information about the surrounding environment. Macrophages have a variety of responses and the information gained from the macropinosome determines which cellular responses to use to further fight any pathogens. Fluorescent chimeras of AktPH-Scarlet (560nm) and Membrane- NeonGreen (488nm) were combined with lattice light-sheet microscopy to understand this vital process in macrophages. To further understand how macropinocytosis is used to perceive a cells environment we induced an inflammatory response using lipopolysaccharide (found on bacterial membrane), a proliferation response using macrophage culture stimulating factor (CSF-1), and finally inhibited macropinocytosis through a PI3-Kinase inhibitor (LY294002). We present new methods of visualizing complex multidimensional data and demonstrate that the elevation of PI3K activity precedes membrane extension and continues during traditional ruffling. The future work will be taking a deep dive into the different phosphoinositols and precisely determining the role of each of the PI’s during macropinocytosis.