Development of Single‐Chain Antibodies Specific to Lysophosphatidic Acid Receptor 2

Abstract

Lysophosphatidic acids (LPAs) are ubiquitous serum phospholipids that trigger diverse cellular responses such as cell proliferation, migration, cell survival, and calcium influx. LPA receptors belong to the G‐protein coupled receptor (GPCR) family, and seven subtypes of LPA receptors have been identified. Among them, LPA receptor 2 (LPA2) is involved in the proliferation and metastasis of ovarian, cervical, and breast cancers. Hence, LPA2‐specific antagonists or antibodies are considered as potential anticancer therapeutics. To develop antibodies against LPA2, a recombinant LPA2 was expressed in Escherichia coli, purified to homogeneity, and immobilized on a solid surface as an active conformation. An M13 phage library displaying single‐chain variable fragments (scFvs) of human IgG containing randomized complementarity‐determining regions was applied to select LPA2‐specific scFv clones. After five rounds of biopanning, a few scFv clones which showed specific binding to LPA2 were identified. Single‐chain antibodies (scAbs), which contain the isolated scFvs and Cκ domain, were constructed and expressed in E. coli. The purified scAbs showed specific binding to LPA2 with KD values of 200–600 nM.