The overarching goal of our lab is to identify new players and establish general principles governing vesicle-mediated cargo transport between intracellular organelles (intracellular vesicles) and between cells (extracellular vesicles).
 

1. New players in vesicle-mediated cargo transport.Trafficking Gene Screen

Cargo proteins in the endomembrane system are transported between organelles by vesicles. Our group focuses on cargo transport to (exocytosis) and from (endocytosis) the plasma membrane. We performed a series of genome-wide genetic screens to dissect mammalian exocytic and endocytic pathways. The screens isolated known trafficking regulators but many genes have not been previously characterized, suggesting that there are still major gaps in our knowledge of membrane trafficking. Currently, we are investigating the molecular mechanisms of new factors identified in the screens using biochemical and biophysical tools, complemented by genetic analysis in cell lines, primary tissues from mice, and cells differentiated from human induced pluripotent stem cells (iPSCs). Through these studies, we aim to uncover novel and general principles – exemplified by the findings of RABIF and AAGAB – governing vesicle-mediated cargo transport.

 

2. Exocytosis in metabolic regulation.

Glut4 Insulin ResponseAnother major goal of our group is to study membrane trafficking in the context of physiology and disease. Exocytosis, in particular, plays key roles in metabolic regulation. Such exocytic pathways include insulin-stimulated GLUT4 translocation, glucose-stimulated insulin secretion, hypoglycemia-triggered glucagon secretion, and nutrient-induced GLP-1 release. Defects in these processes are closely linked to metabolic disorders such as insulin resistance and type 2 diabetes. We primarily use GLUT4 translocation as a paradigm to elucidate the molecular basis of these metabolic exocytic processes. Our group developed a unique combination of genetic screens and biochemical reconstitution to identify and characterize new regulators of GLUT4 trafficking. Our long-term vision is to map the entire protein-protein networks that mediate and regulate GLUT4 exocytosis and endocytosis. Meanwhile, we aim to understand how the networks are compromised in insulin resistance and type 2 diabetes.

 

3. Cell-to-cell cargo transport mediated by extracellular vesicles.

While intracellular vesicles transport cargo between organelles within cells, extracellular vesicles (EVs) transport cargo molecules, such as proteins and RNAs, between cells. EV-mediated transport plays important roles in cell-to-cell communication and propagation of pathogenic molecules (e.g., Aβ in Alzheimer’s disease). Cargo transport mediated by EVs is comprised of two sequential steps – EV release from donor cells and EV entry into recipient cells – both of which are tightly linked to exocytosis and endocytosis. We are still at the very beginning of understanding the molecular basis of EV-mediated transport, a frontier in membrane biology research poised to revolutionize biomedicine. In collaboration with the Stowell lab, we are developing new biochemical and genetic platforms to dissect EV release and entry, capitalizing on our experience in intracellular membrane trafficking.

iPSC


Acknowledgements 

We are grateful to funding agencies that generously support or supported our work: 

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

National Institute of General Medical Sciences (NIGMS)

National Institute on Aging (NIA)

American Diabetes Association

Pew Charitable Trust

American Heart Association

University of Colorado Cancer Center

Cancer League of Colorado

Linda Crnic Institute for Down Syndrome

University of Colorado Boulder