Donald F. Steiner (1930 – 2014)

Donald F. Steiner

Donald F. Steiner, the distinguished professor emeritus at the University of Chicago who elucidated the mechanism of biosynthesis of insulin from proinsulin, died Nov. 11 at age 84.

Insulin is a small and beautifully organized protein with a unique two-chain structure. It was the first protein to be sequenced, which led to Fred Sanger’s first Nobel prize in chemistry.

There was much speculation about how the two chains were assembled, but the mystery was solved after the discovery of proinsulin. Proinsulin was the first of the prohormones (including proglucagon, proparathyroid hormone and proopiomelanocortin) and proproteins such as proalbumin.

Diabetes mellitus is an increasingly common disease that results from inadequate insulin production (Type I) or inadequate insulin signaling (Type II), and Steiner’s work led to a better understanding of these disorders and to their improved treatment.

After graduating from the University of Cincinnati with his bachelor’s in chemistry and zoology, Steiner earned a master’s degree and medical degree at the University of Chicago School of Medicine in 1956. As a medical student, he worked with Herbert S. Anker in the biochemistry department and studied the biosynthesis of antibodies in rabbit spleen explants, for which Steiner received his master’s degree. This work was published in the Proceedings of the National Academy of Sciences, with Steiner as first author, a harbinger of his scientific acumen. He then did an internship at the University of Washington and spent three years in the laboratory of Robert H. Williams, an endocrinologist who was also the chairman of the department of medicine. Steiner’s work centered on the mechanism of action of oral hypoglycemic agents.

Earl A. Evans Jr., the chairman of the biochemistry department at the University of Chicago, offered Steiner the position of assistant professor in 1960. Steiner had not applied for the position, and the offer came out of the blue. The starting salary of $9,000 ($71,000 in today’s dollars) was much more that he could have made as a medical resident or a postdoctoral associate, which Evans emphasized as an inducement (if one were needed). To add perspective, tuition at the University of Chicago School of Medicine was $999 in 1960 ($7,900 in today’s dollars), which contrasts with today’s tuition of $47,673 for three quarters. Steiner began his new job in September 1960.

Steiner initiated his own studies on the action of insulin on carbohydrate metabolism and glycogen biosynthesis at Chicago. His work demonstrated that insulin led to dramatic increases in glycogen content, RNA synthesis and protein synthesis in diabetic rats. His work in the early 1960s showed that insulin regulates the rate of synthesis of several proteins involved in glycolysis and gluconeogenesis in vivo.

Before moving to a high-rise apartment on Chicago’s Gold Coast, Steiner lived in an apartment near the university. At a chance meeting at an elevator with a medical student who lived in the same building (Nicholas A. Vick), Steiner asked to be alerted if a patient with an insulin-secreting adenoma was admitted to Billings Hospital. Serendipity intervened several months later: Such a patient was admitted, and Steiner retrieved about half of a one-gram tumor and incubated portions of it with [3H]-leucine and [3H]-phenylalanine.

Steiner commented later that he had no preconceptions about how this work would develop. He had no grant for these studies and no working hypotheses to test. Because he had no experience in this line of experimentation, he knew that he would not have been funded initially for such experiments. After acid/ethanol extraction of the pancreatic tumor, gel-filtration chromatography revealed radioactive a, b, and c peaks. Component a included high-molecular-weight material, and component c was insulin. There were no lower-molecular-weight peaks corresponding to the two chains of insulin. Component b was a protein of high specific activity that reacted with insulin antisera and was readily converted into insulin after treatment with trypsin. Component b was the biosynthetic precursor of insulin, and it was named proinsulin.

Proinsulin begins with the B-chain, followed by the connecting peptide, and ends with the A-chain. Proinsulin is processed in the trans-Golgi, yielding the connecting peptide and insulin with its A- and B-chains attached by two disulfide bonds. In response to glucose and other agents, insulin and connecting peptide are co-released from pancreatic β-cells. Arthur H. Rubenstein (formerly dean of medicine at Mount Sinai School of Medicine and the University of Pennsylvania) and Kenneth S. Polonsky (currently dean of medicine at the University of Chicago) were early collaborators who studied the secretion of connecting peptide along with insulin under a variety of clinical conditions.

The identification of the physiological enzymes involved in the conversion of proinsulin to insulin required more than 20 years of effort from many laboratories. This work started in the 1970s with the discovery that Kex2p in yeast is required for the production of α-mating factor. This eventually led to the discovery of the kexin/subtilisin-like prohormone convertases 1/3 and 2 as participants in the proteolysis at paired basic amino acid residues that led to the cleavage of the connecting peptide. This is followed by the action of carboxypeptidase E to eliminate basic amino acids, yielding mature insulin with its A- and B-chains.

Steiner made significant contributions in deciphering the physiology of insulin biosynthesis as well as in the pathology of diabetes, a disease that affects some 29 million Americans. Frederick Banting and Charles Best discovered insulin in canine pancreas in Toronto in 1921. Insulin extracts from bovine or porcine pancreas treated diabetes for more than 60 years. A new era began in the 1980s when human insulin was synthesized for therapeutic use. In 1982, recombinant A- and B-chains were expressed in E. coli and combined chemically to produce molecular insulin. Since 1986, human insulin has been prepared from recombinant proinsulin followed by treatment with trypsin and carboxypeptidase B. This is the form of insulin that is prescribed in the United States today, and the methodology for its preparation is a direct consequence of Steiner’s work.

I joined Steiner’s laboratory in 1961 as an M.D./Ph.D. student and left in July 1966 to work in the U.S. Air Force Medical Corps; unfortunately, I did not participate in the proinsulin saga. I wrote my dissertation and returned to the university in 1968 to defend my work and receive the Ph.D. Steiner was an exacting mentor who thought that any dissertation should undergo the review and scrutiny of a paper (or papers) submitted to the Journal of Biological Chemistry. After extensive discussions and rewrites to obtain his endorsement, gaining the approval of the dissertation committee (Herbert S. Anker, Eugene Goldwasser and Wolfgang Epstein) was a cakewalk.

At first, Steiner’s career developed slowly. After six years as an assistant professor, he was promoted to associate professor in 1965. Just a year later, he was promoted to professor after the discovery of proinsulin (even though the dust had not yet settled concerning the validity of this biosynthetic process). A promotion after such a short time was and is very unusual. Evans most likely did not want to lose Steiner to Harvard University as he had lost Konrad Bloch and Eugene P. Kennedy. Steiner received many offers for positions elsewhere, but he valued his colleagues and chose to remain at Chicago for his entire professional career. Evans emphasized research for both graduate students and faculty members, and he held course work for both to a minimum, an educational and scientific strategy with which Steiner agreed. This tradition has held since its earliest days, when Maude L. Menten received her biochemistry doctorate in the department.

Steiner was soft-spoken, and his outlines for lectures or seminars contained the directions “speak louder” interspersed throughout. He was a person of even disposition who never raised his voice under circumstances that would readily elicit expletives from others. He was an efficient and prolific worker who also had time for activities in the arts, especially music.

In 1964, a National Institutes of Health site visit team reviewed the application of Lloyd M. Kozloff, whose laboratory was two doors away. In the afternoon, Kozloff gave the visitors a tour of the department. They entered the main lab, where I was working with Judith King, a superb technician who was co-author on several Steiner papers. Then they walked into Steiner’s office, where he was kneeling on the floor fabricating a harpsichord. Kozloff won the grant despite this encounter.

Steiner received the University of Chicago’s Alumni Award in June. This is the highest award that the university gives. For anyone interested in a more complete description of the proinsulin story including numerous blind alleys and technical difficulties, see Steiner’s “Reflections” article (“Adventures with insulin in the Islets of Langerhans”) in the JBC.

Robert Roskoski Jr. is the scientific director at the Blue Ridge Institute for Medical Research in North Carolina.