The major goal of Dr. Hinkle's research is to understand how hormone binding to a plasma membrane receptor triggers a characteristic sequence of cellular responses. Activation of the TRH receptor, which is coupled to G proteins, stimulates phosphoinositide turnover and increases cytoplasmic calcium and protein kinase C activity by well established pathways, but TRH stimulates other kinase cascades by pathways that are currently unknown. Cultures of pancreatic islet cells are used to study the molecular mechanisms involved in regulation of insulin secretion by glucose and other agents. Calcium is a key regulator of exocytosis and transcription in both of these model systems. In order to dissect the complex calcium response to hormones, several fluorescence imaging techniques are used to monitor the free calcium concentration in the cytoplasm and endoplasmic reticulum of individual cells.
Many studies focus on how specificity in signaling is achieved.
The intracellular signals generated by hormonal activation are transient, and cells undergo rapid and selective desensitization following exposure to hormone. Current work also attempts to understand the mechanisms responsible for the desensitization process. Mutant receptors, dominant-negative mutants of proteins involved in signaling and trafficking, and cells from knockout mice are used in these investigations. Signal transduction, desensitization and recovery of the thyrotropin-releasing hormone receptor after inhibition of receptor internalization. Fluorescence methods to assess multidrug resistance in individual cells.