Following his PhD, Lemmon was a
postdoctoral researcher and fellow of the
Damon Runyon Cancer Research Foundation at
New York University in the laboratory of
Joseph Schlessinger. With Kathryn Ferguson and others, he also played an important role in understanding the structure and function of the
Pleckstrin homology domain in phosphoinositide signalling and elsewhere. Lemmon has made important contributions to the discovery of both normal and pathological activation mechanisms of growth factor receptors and the signalling networks that they engage within cells. He is also committed to exploiting this understanding clinically. These receptors and their downstream effectors are activated aberrantly in numerous cancers, and are important targets of cancer drugs. Lemmon's recent work has focused on the need to understand the biochemistry of
oncogenic activation to use such drugs effectively. His research has been funded by the
National Cancer Institute, the
National Institute of General Medical Sciences, and the Department of Defense Congressionally Directed Medical Research Programs. Lemmon serves on the
editorial boards of several scientific journals, including
Cell,
Molecular Cell,
Molecular and Cellular Biology, and
Science Signaling. Having served as an associate editor for the
Biochemical Journal for many years, he was appointed chair of the editorial board in January 2021. Between 2007 and 2013, Lemmon served as secretary for the
American Society for Biochemistry and Molecular Biology (ASBMB). ==Awards and honours==