Challenges and Potentials for New Drug Discovery
The membrane of a cell functions not only as a border, but also as an interface between the cell and the external environment. Membrane proteins embedded within the cellular membrane serve a critical purpose in the maintenance of many cellular functions including: signal transduction, cell integrity, intracellular and extracellular transport and cell-to-cell communication. Given their importance in cellular communication and transportation of molecules and ions across the cell membrane, membrane proteins form the largest category of druggable targets studied in the pharmaceutical industry. In fact, approximately two-thirds of currently available therapeutic molecules target one or more membrane proteins, yet these account for only 7% of the underlying targets. With new targets for drug discovery emerging at a rate faster than they can be screened and tested, membrane proteins remain a dominant focus for new drug discovery programs.
Challenges for Expression of Membrane Proteins
Studying membrane protein structure and function for drug characterization and optimization brings a unique set of challenges to laboratories. To begin with, structural conformation of membrane protein is largely dependent on interaction with the cellular lipid membrane. There are three distinct regions that characterize transmembrane proteins, including:
- The extracellular domain
- The domain embedded within the hydrophobic region of the membrane bilayer
- The intracellular domain
All three regions work in concert to either 1) sense and initiate signals that are responsive to the external environment or 2) control the exchange of materials across the cell membrane. Despite the fluidity of the cell membrane, the orientation of membrane proteins within the cell membrane remains constant. Thus, the extracellular domain of the transmembrane protein is always outside the cell and the intracellular portion is always inside.
Due to the requirement of membrane proteins to associate with cellular membranes, expression of membrane proteins in heterologous systems can be challenging. Often, cellular expression of recombinant membrane protein can result in protein aggregation and misfolding due to the hydrophobic nature of the transmembrane segments. Efforts to use live cell systems or membrane preparations derived from cells can help to ensure structural stability of the membrane proteins, however, application of these approaches is limited by low target protein concentration, receptor heterogeneity and lipid contaminants; all of which can contribute to poor sensitivity and high experimental variation.
Challenges for Antibody Production against Membrane Proteins
Antibodies that recognize conformation-dependent epitopes on membrane proteins are highly valuable tools in most stages of drug development. They may be used as therapeutics or diagnostics given their ability to bind receptor regions that are critical for function or to detect proteins located on the cell surface. Unfortunately, production of antibodies against multispanning membrane proteins, such as G protein-coupled receptors (GPCRs), is extremely difficult using conventional approaches.
This is largely due to three main factors:
- Most epitopes require the membrane for structure and purification. Strategies to remove the membrane to obtain pure material often denature the protein and destroy the epitope; and while immunizing with whole cells expressing the protein of interest can circumvent this issue, the immune response to an impure mixture of proteins is often profoundly diminished.
- The epitopes are made up of small, discontinuous segments, which present major obstacles to standard peptide or recombinant protein technology as these segments cannot fold or assemble together.
- Lastly, efforts to express membrane proteins often result in very low levels of protein making it highly difficult and time-consuming to produce sufficient material for immunization.
GenScript's Innovative Strategies for Membrane Protein Antibody Discovery
As a pioneer and leader in antibody production, GenScript's experienced antibody team combines years of extensive optimization and state-of-the-art technology into a well-established membrane protein antibody development platform for the generation of specific antibody binders and functionally active antibodies against membrane proteins. After proper target analysis, our antibody experts will suggest a customized antibody production protocol, utilizing our collection of innovative strategies for successful membrane protein antibody production. GenScript has extensive experience and successful cases in generating therapeutic antibody leads and tool antibodies against single transmembrane proteins (i.e. immune checkpoint family members) and multiple transmembrane proteins (i.e. GPCR family members and ion channels). See below.
|DNA Immunization technology||Allows antigen production to occur in vivo, bypassing the need to produce and purify membrane protein antigen in vitro.|
|Alternative antigen design options||DNA, extracellular domain (ECD), peptide, over-expressing cells, or a combination of which may be used for immunization to elicit functionally active antibodies against difficult membrane protein targets.|
|ImmunoPlus antigen modification technology||Designed to break immune tolerance to produce antibodies against high-homology GPCR targets.|
|Optimized high throughput screening||Capture ELISA, FACS and FMAT are used to directly select the antibodies that recognize cell surface targets in their native conformations.|
Membrane Protein Related Services
For membrane protein antibody development, check out GenScript's custom monoclonal and polyclonal antibody development packages.
- DNA Immunization Services – ideal tool for antibody production against problematic antigens, including membrane proteins, toxic proteins, unstable proteins, etc.
- Custom mAb Services – Fully customizable mAb development packages tailored to meet your specific needs.
- Custom pAb Services – Fully customizable pAb development in a variety of species with multiple purification options available.
Our PhD level technical account managers can assist you in custom designing the optimal package to meet your specific needs.
Our customer service representatives are available 24 hours a day, Monday through Friday to assist you.