By Leah Mann
The labs of Wenbiao Chen, associate professor of molecular physiology and biophysics, and Irina Kaverina, professor of cell and development biology, recently published a study in Molecular Metabolism focused on detecting genes that regulate insulin secretion. The authors demonstrated a new role for the Commander complex—a bound group of 16 proteins—in insulin granule docking. Through this process, secretory vesicles storing insulin attach to the cytoskeleton near the plasma membrane when glucose levels are stable. As the Commander complex increases the adhesion of the secretory vesicles, it also enhances basal insulin secretion.
We sat down with Chen to find out more about this research.
What issue/problem does your research address?
While strides have been made in the field of insulin research, most studies have focused on glucose-stimulated insulin secretion rather than basal insulin secretion. Glucose-stimulated insulin secretion refers to insulin secretion that is mediated by products of glucose metabolism, while basal insulin secretion refers to insulin secretion in fasting conditions without external factors. Our research tackles this gap by addressing insulin secretion in pancreatic beta cells, especially during fasting (when blood glucose is at basal levels) or during continuous glucose supply.
What was unique about your approach to the research?
We developed a beta cell line that allows for CRISPR and for us to conduct a high-throughput assay looking at insulin secretion in populations as well as in single cells. High-throughput screening grants us the opportunity to conduct many tests and distinguish individual cells. Previously, high-throughput methods for analyzing single-cell secretion in beta cells did not exist, which prevented the application of CRISPR to study insulin secretion. Using our new system, we performed a genome-wide CRISPR screen to identify genes that regulate insulin secretion.
What were your findings?
We found that the Commander complex, an evolutionarily conserved complex that retains similar protein sequences across species, regulates low glucose insulin secretion by helping to target insulin-containing vesicles close to the secretion sites. The Commander complex contributes to the recycling of integrin β1, a transmembrane receptor that promotes cell adhesion. By doing so, it increases the number of docked insulin granules and thus facilitates insulin secretion.
What do you hope will be achieved with the research results in the short and long terms?
This proof-of-principle study not only identified a novel pathway that regulates basal insulin secretion, but also laid a pathway for identifying other regulators of insulin secretion.
What are the benefits of this research?
This work provides a deeper understanding of the regulation of insulin secretion, which may uncover therapeutic targets for diabetes, a chronic disease afflicting more than 10 percent of adults.
Where is this research taking you next?
We plan to use CRISPR screening to identify other genes and pathways that regulate insulin secretion and to address several long-standing questions related to regulated secretion. For example, secretion delivers membrane-packed contents in secretory granules from inside of the cell to the outside by merging the granule membrane to the cell membrane. How secretory cells maintain their surface area and granule pool during high activity is not well understood.
This work was funded by a Vanderbilt Discovery Grant and multiple National Institutes of Health grants.
The paper “Genome-wide CRISPR screen identified a role for commander complex mediated ITGB1 recycling in basal insulin secretion” was published in Molecular Metabolism in September 2022.