Biogenesis of secretory granules in neuroendocrine cells
Previous and Current Research
A long-standing interest in the laboratory has been to understand how cells control the formation of intracellular vesicles and compartments, in particular regulated secretory granules. Regulated secretory granules contain bioactive hormones, in addition to proteins which are involved in prohormone maturation and exocytosis. Using neuroendocrine cell lines as models systems, we have studied the biogenesis of secretory granules. After formation from the Golgi complex, the secretory granule is refined and remodelled by homotypic fusion and clathrin-mediated vesicle budding, in a process called maturation. Maturation is highly regulated and results in the production of secretory granules with a precisely defined composition. Perturbation of maturation results in secretory granules with both an abnormal composition and function. Understanding the underlying molecular connection between maturation and function is an important goal in the laboratory.
Recent research in the laboratory expands the interest in protein trafficking and organelle biogenesis into understanding the formation of autophagosomes. Autophagy ("self-digestion") is a nutrient sensitive cell survival response. Upon starvation, autophagosomes form, sequester cytosolic components and mature by fusion with endosomes into degradative compartments. The degradation of the sequestered components allows a temporary replenishment of intracellular levels of amino acids. Autophagy has also been implicated in embryogenesis and development of a tumorigenic phenotype, and is likely to be an important survival pathway.
A common approach is used in both systems utilising cell free reconstitution experiments, i.e. in vitro fusion assays, coat recruitment and vesicle budding assays, siRNA screens as well as targeted knock down by siRNAs, supported by conventional biochemical and molecular tools.
Future projects
The identification of key molecules provides us with the chance to study the regulation of their function. Ultimately, understanding the regulation of organelle biogenesis will allow a better understanding of this process in normal cells, and provide tools for the study of organelle biogenesis in diseased cells where this process is not functioning correctly.
