Commentary-How do we Improve Training for Receptor Research?
Marilee Ann Benore
DOI : 10.3844/ajbbsp.2015.182.184
American Journal of Biochemistry and Biotechnology
Volume 11, Issue 4
This issue of the American Journal of Biochemistry and Biotechnologyfeatures articles about receptor-ligand interactions that are critical to thewellbeing of all living organisms. The importance of the field of receptorresearch is supported by the large number of articles published in journals,the numerous specialty journals, the international conferences and thepercentage of legal drugs on the market that target receptors. There areseveral journals dedicated to receptor or ligand study, including those inbiochemistry, pharmacy and synthesis. Both large and small conferences havesessions devoted in part or completely to the topic. There are over 1 millionhits in response to the query “receptor” and over 4 million to the query “drug”in PubMed (as of July, 2015). (http://www.ncbi.nlm.nih.gov/pubmed).
Most drugs approved foruse in humans target receptors. In their Nature Reviews paper entitled“Drugs, their targets and the nature and number of drug targets”, Imming andcolleagues examined drug targets, characterizing the drugs in consideration ofthe human genome (Imming et al., 2006). They developed a detailed classification system: Defining a target as amolecular structure that undergoes an interaction with a chemical that isconnected to a clinical effect. Eight physiological target categories weredescribed: Enzymes; receptors; ion channels; transport proteins;DNA/RNA/ribosome; monoclonal antibodies; substrates, metabolites and proteins;and various physicochemical mechanisms.
Thistopic was further explored by Rask-Andersen and others in the 2011 NatureReview article “Trends in the exploitation of novel drug targets” (Rask-Andersenetal., 2011). Theyanalyzed the US Food and Drug Administration (FDA) approved drugs as well asthe DrugBank database to determine trends in drug development and approval (http://www.drugbank.ca/). Their curatedlist of 989 drugs with therapeutic effects on 435 targets resulted in thefollowing data about the targets: Receptors account for 44%, transporters 15%,enzymes 29% and the category of “other” 12%. Thus, the inclusion of receptorsand transporters accounts for more than half of the drugs approved by the FDA.Since even drugs that stimulate enzyme cascades often first interact withreceptors, ion channels or membrane carriers, the significance ofreceptors in physiology is clear.
Yet few undergraduate students of biology, chemistry orbiochemistry are trained to study receptors or kinetic methods unless they haveresearch experience. They study similar and related topics: Students inchemistry study the stoichiometry of reactions and equilibria, while biologystudents study the product formation of enzymes. But many students are unableto predict how many receptors will be saturated if the ligand concentration isthe same as the binding affinity of a given receptor. The emphasis on catalysisis understandable because metabolism, which is dependent on enzymes, has been adominant theme in physiology and biochemistry courses. Student in abiochemistry course can relay the details of Michaelis-Menten kinetics, yet fewrecognize the name Scatchard (Michaelis and Menten, 1913; Scatchard, 1949). Ofcourse, students in neuroscience or prepharmacy programs are more likely tolearn about receptors, agonists and antagonists. The emerging significance of homeostasis will likely increase curricular content ofreceptor mechanisms. In addition, the focus on skills should help developstudents with the mathematical and laboratory expertise to devise experimentsstudying receptors (White et al., 2013). (See the updatedguidelines for Biochemistry education at www.asbmb.org).
While the information about receptors in courses, textsand lab experiences provide examples there is often little theory and limitedapplication. Chapters in texts focus on the outcomes of the processes, such astransport of water molecules across a membrane, receptor-mediated endocytosisof the LDL receptor and second messenger actions. Unlike enzymes, there isminimal detail on the experimentation, the classic research or kinetic aspects.There are relatively few new books dedicated to the topic, with the exceptionsbeing the well-known pharmacology texts by Goodman and Gilman and by Foremanand Johansen. The surge in neurology research has led to more medically relatedtexts, such as by Allen. Many of us still use the old texts available, such asYamamura et al. (1976) or my personal favorite, the long out-of-printQuantitative Problems in the Biochemical Sciences by Montgomery and Swenson(Table 1).
So how do we preparethe next generation of scientists who will be excited about and qualified tocarry out this research? We begin by including more examples in the class andlaboratory experiences of students. If a student can learn rudimentarycatalysis, it is a relatively easy matter to study simple receptors due to thesimilarities: Saturation, binding affinity and assay development(Benore-Parsons and Sufka, 2001).
Lecture courses should include more examples and problems to testunderstanding. Excellent articles are available on incorporating topics, suchas those in education journals (Sears etal., 2007). Case-based and problem-based learning provide relevantexamples. The National Center for Case Study Teaching in Science maintains aweb site for examples (see http://sciencecases.lib.buffalo.edu/cs/collection/).Problems that incorporate descriptions of the methods or specific drug targetsare especially helpful.
Theuse of a “theme” or “threaded” topic during the semester is also useful inproviding a continuous example and full picture of receptor mechanisms. Forexample, this method has been successfully used to teach entire courses usingthe AIDs virus or other topics as the thread (Grover, 2008; Casselton et al., 2008; White, 2002). In mynon-major biochemistry class I incorporate a threaded topic, using insulin asthe example woven through the topics all semester. Over the term students learnabout insulin protein structure, the history of its discovery, it’s function,gene and receptor. The development of ELISA techniques and binding ofrecombinant versions to the receptor are investigated. Students are surprisedthat insulin is both a ligand and a protein and this leads to discussions aboutsite-directed mutagenesis, recombinant insulin versions and binding affinitiesof the insulin analogues to the receptor. Signaling systems and post-receptoractivation is another concept to explore. An additional useful example is todetail the processes of drug development and Food and Drug Administrationapproval for medications used in humans. Currently, there is a tremendousincrease in the abundance of protein sequence information and in many cases cleardocumentation of sequence variations that exist for receptors in the humangenome. Thus, an important topic would be mutations of the insulin receptorthat can lead to diabetes. The threaded series of related topics provides anoverview of the many approaches used in receptor research.
Laboratory experience is just as valuable, indeed essential. In myadvanced biochemistry laboratory course the focus was on ligands, receptors andtransporters. Students learned to carry out ELISA experiments using a BioRadkit. We followed the Bio Rad quantitative protocol with a second set of studentdesigned experiments. Their goal was to investigate the impact of physiologicalagents on the accuracy of the ELISA and identify drugs that might interferewith the activity and accuracy of the assay. Students write up the conclusionsas if they were testing the system for a law case to render results inaccurate.Following this experiment, students studied binding and competition using theavidin-biotin system, with HABA as a competing agent (Ninfa et al., 2009). Finally, they purifiedand characterized the transport protein Riboflavin Binding Protein, easilymonitored by the bright yellow of theriboflavin ligand, using a modified version of the literature protocol (Millerand White, 1986). Problems and quizzes accompanied the experiments to ensureunderstanding. By the end of the term students were well versed in how topurify and characterize a protein, determine binding affinity using Scatchardplots and carry out competition curves.
Table 1.Textbooks and resources for learning about receptors and ligands
· Textbook ofReceptor Pharmacology, Third Edition (2010) John C. Foreman (Editor), TorbenJohansen (Editor),CRC Press, BocaRaton, Fl
· Signaling byReceptor Tyrosine Kinases (Subject Collection from Cold Spring HarborPerspectives in Biology) (2014)
JosephSchlessinger and MarkA. Lemmon (Editors) Cold Spring harbor Press, Cold Spring harbor, MA
· Receptor Based Solutions; Functional Neurology Every Doctor Should Know (2014) Michael D.Allen, Healthbuilders Publishing
· Goodman andGilman's The Pharmacological Basis of Therapeutics, Twelfth Edition(2011) Laurence L. Brunton, Bruce A. Chabner, Björn C. Knollmann, McGraw-HillCompanies, China
· Neurotransmitterreceptor binding. (1978) H.I. Yamamura, S. J. Enna and M. J. Kuhar, Editors,Raven Press, New York
· Quantitative problems in the biochemical sciences, 2ndedition (1976) R. Montgomery and C. A. Swenson, W. H. Freeman, San Francisco,CA
Finally,what can researchers do to improve the training of future scientists? Thosescientists immersed in receptor research should participate in education.Internships, research experiences and opportunities in academics or in industryshould be made available to students interested in pursuing these careers (Callier et al., 2014).Researchers in industry should make the effort to offer to give seminars atlocal Universities, or host site visits.
With these efforts, thenext generation of researchers will be prepared to innovate and collaborate indrug, ligand and receptor discovery and characterization.
The author thanksLawrence Wennogle for critical reading and suggestions. The author notes thatDr Wennogle was her postdoctoral advisor and is a co-author on publications(not cited). The author thanks George Garcia for suggestions.
The author disclosesthat she is the one of the team of authors of the laboratory manual referencedin the article. The author notes that she is a member of the core team workingwith the ASBMB, but has no financial conflict. The author has no otherfinancial conflicts. There is no funding support to acknowledge.
The author wrote the article with input as indicated in theacknowledgements.
This article isoriginal and contains unpublished material. The corresponding author confirmsthat all of the other authors have read and approved the manuscript and noethical issues involved.
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© 2015 Marilee Ann Benore. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.