Cells have compartmentalized structures and rely on regulated membrane trafficking to move cargo between organelles/compartments. Many essential cellular processes such as nutrient uptake, receptor mediated signaling and synaptic vesicle recycling depend on membrane trafficking and endocytosis. Our lab is interested in the role of actin cytoskeleton and actin associated proteins in membrane trafficking and endocytic mechanisms in cells. Recently, we demonstrated that nonmuscle myosin II (MII), an actin associated motor protein, is critical for both compensatory and constitutive receptor mediated endocytosis in neurons and fibroblasts. Our work provided the first cellular and genetic evidence for the importance of actin-MII interactions during early stages of clathrin coated vesicle formation. Our current model is that MII regulates endocytosis by forming a contractile network with actin around the site of membrane remodeling and acting like a purse string to regulate the curvature and scission processes, thereby aiding in vesicle budding (Fig.1). Identifying MII as a critical player in endocytosis has raised the following questions:
Our work on primary neurons indicates that MII-driven tension/actin dynamics regulate the major pathway of synaptic vesicle retrieval (clathrin mediated compensatory endocytosis) and is critical for synaptic transmission. This suggests a unique and essential role for actin-MII mediated tension in cell types that require rapid and continuous membrane remodeling to perform essential organ function. We are interested in understanding the cell type specific requirements for dynamic cytoskeletal changes in cells that populate organs like kidney and brain.
To answer these questions, we employ animal and cell culture model systems. We use advanced microscopy techniques like live cell confocal imaging to monitor dynamic changes in recruitment/uptake and endosomal/lysosomal processing of fluorescently tagged ligands and receptors, clathrin coated pit markers, membrane markers, etc. We also use TIRF microscopy to analyze live surface membrane dynamics in various cell types (Fig.2). The basic knowledge and insights obtained from our work on these fundamental cellular processes might provide mechanistic understanding of trafficking related diseases, certain renal diseases and MYH9 related disorders.
Contact Information for the Chandrasekar Lab:
Indra Chandrasekar, Ph.D.
Assistant Scientist, Sanford Children's Health Research Center
Sanford Research Center, Room 2250
2301 E. 60th Street North
Sioux Falls, SD 57104