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Genetic Engineering & Biotechnology News | GENengnews.com | SEPTEMBER 1, 2016 | 19 sensitivity, the MPA uses flow cytometry for single-cell detection, enabling the elucidation of both primary and secondary binding tar- gets. Because the MPA expresses each mem- brane protein directly within living cells, it can be used to identify the targets of many types of interactions that require functional readouts based on cellular activity. Besides antibody targets, the MPA can identify the receptors of natural protein ligands, toxins, and viruses. Antibody Specificity Profiling The MPA was initially validated by test- ing the specificity of antibodies with known membrane protein targets. The therapeutic antibody rituximab (anti-CD20) and a lead candidate antibody against an ion channel (anti-P2X3) were tested for reactivity against the MPA (Figure 2A). The known target for each of these antibodies was readily identi- fied, with signals 20- to 60-fold higher than background. For the anti-P2X3 candidate, the MPA also identified binding to an ad- ditional membrane protein, informing the final lead selection in this program to avoid off-target binding that could cause patient side-effects. Antibody Target Identification In the course of developing antibodies against membrane proteins, Integral Mo- lecular has identified hundreds of orphan an- tibodies that are highly reactive with human membrane proteins but whose specificities are not yet known. The MPA was used with several of these antibodies to successfully identify their molecular targets (Figure 2B). Intriguingly, several of the targets identified (e.g. CD151) are multispanning membrane proteins (that traverse the plasma membrane multiple times), which are the most difficult types of membrane proteins to express and target. These types of studies are resulting in novel therapeutic targets and new disease biomarkers. Identification of Novel Viral Receptors The systematic array of the membrane proteome in live human cells provides a unique opportunity to test the function of each membrane protein in live cell-based as- says. For example, putative cellular receptors for Zika and Ebola viruses were identified by infecting MPA-expressing nonpermissive cells with viruses that encode a fluorescent reporter protein, identifying membrane proteins that enable viral entry and infection (Figure 3). The identification of novel receptors for Zika and Ebola viruses is resulting in new intellec- tual property and new therapeutic strategies for combating these pathogens. Conclusion The MPA represents a rapid, compre- hensive, and highly sensitive platform for identifying the membrane protein targets Enabling Epigenetics Research PROTEINS AND SUBSTRATES FOR EPIGENETIC DRUG DISCOVERY Active Motif offers a large collection of high quality proteins and histone substrates for epigenetic drug discovery, including: > Nucleosomes > Modified Histones > Epigenetic Enzymes > Reader Domains ASK FOR A QUOTE: activemotif.com/epiproteins activemotif.com Duncan J. Huston-Paterson, D.Phil., and Soma S.R. Banik, Ph.D., are in scientific communications, and Benjamin J. Doranz, Ph.D. (bdoranz@integralmolecular.com), is president and CSO of Integral Molecular. Website: www. integralmolecular.com. of a wide variety of antibodies, protein ligands, and functional interactions. The platform has been validated for use in determining target specific- ity, deorphaning antibodies, and identifying viral receptors, thereby de-risking lead candidate selec- tion, establishing new intellectual property and fa- cilitating the discovery of new disease targets. DRUG DISCOVERY Tutorial Figure 3. Integral Molecular's Membrane Proteome Array was used to identify human membrane proteins that act as receptors for Zika and Ebola viruses. Shown is one 384-well microplate from the screening of each virus.