A committed academician and researcher, Dr. Stull has contributed extensive professional and academic service to his field and the university and is the holder of the Fouad A. Bashour Distinguished Chair in Physiology. Dr. Stull's research involves the cellular and molecular basis of how contraction of muscle cells occurs in response to chemical signals from nerves and hormones. The motor protein, myosin initiates movement in all cells in the body by tracking on actin filaments. Myosin activity is enhanced by the calcium-dependent by myosin light chain kinase which phosphorylates a regulatory subunit of myosin while myosin light chain phosphatase dephosphorylates the light chain. Impaired light chain phosphorylation causes heart failure, and failed smooth muscle functions involving the hollow organs of the body (blood vessels, airways, intestines, and bladder). The phosphorylation of myosin is not a simple cascade but is controlled by different integrative signaling modules forming cellular networks with different second messenger systems. 

His work is directed to understanding how kinase and phosphatase activate the myosin motor in muscle cells in relation to chemical signals controlling the networks. He has discovered two new kinases in heart muscle that may be key regulators of its myosin motor protein. One kinase, cardiac myosin light chain kinase is greatly elevated in diseased heart and thus, may be recruited to enhance myosin function to help the heart pump blood. He has established that this kinase is essential for the basal phosphorylation of myosin and maintenance of heart performance. Another newly identified kinase may be recruited to phosphorylate myosin with stresses acting on the heart during disease states. 

He has also established that all smooth muscles of the body require myosin phosphorylation by a smooth muscle specific myosin light chain kinase. This phosphorylation is necessary for control of blood pressure by smooth muscle cells in blood vessels, movement of digested food in the stomach and intestines, maintenance of airways in the lungs and emptying of the urinary bladder. We have investigated interconnected chemical networks that affect myosin phosphorylation using genetically modified mice with biophysical, biochemical and physiological measurements. Primary hypotheses are directed to identifying the key signaling proteins essential for smooth muscle contraction that may contribute to the development of different smooth muscle based diseases, including our recent observation that mutations in the gene of smooth muscle myosin light chain kinase causes aortic aneurysm and dissection in humans.