Probing GPCR conformation in cell by chemical crosslinking and mass spectrometry

Authors

• BX Huang
• J-W Lee
• H-Y Kim

Abstract

The activation of G protein-coupled receptors (GPCR) mediates a variety of important biological signals. GPR110 belongs to the adhesion GPCR class with distinctively long N-terminus. Although GPR110 is an orphan receptor with unknown ligand, it has been identified as an oncogene implicated in lung and prostate cancers. In an effort to understand the molecular basis of GPR110 activation, we probed GPR110 conformation in living cells using chemical crosslinking and mass spectrometry. HEK cells overexpressing HA-GPR110 were incubated with disuccinimidyl suberate (DSS, a lysine-specific crosslinker). The DSS-modified HA-GPR110 was pulled-down and subjected to SDS-PAGE, tryptic digestion, and nanoLC-ESI-MS/MS. The MS-based approach identified 17 crosslinked lysine pairs in the N-terminal domain of GPR110. Among them, K29-K38, K187-K240, K240-K254, K398-442, K398-K438, K398-K427, K427-K442, K427-K438, and K151-K442, resulted from through-space crosslinking between two peptide segments, while K31-K32, K38-39, K70-73, K151-K157, K235-K240, K438-K442, K427-K432, and K432-438, were cross-linked within a single peptide segment (loop-links). In addition, a through-space crosslinking between the intracellular loop III (IL3) and the C-terminus (K783-K852), and 4 loop-links (K864-K873, K852-K860, K860-864, and K875-K878) in the C-terminal region were identified. The data indicated that the alpha carbon distance between each crosslinked lysine pair is within ~24 Å, the maximum crosslinking length of DSS. Our results represent the first experimental data for the three-dimensional structure of GPR110 in living cells. This strategy should be useful in probing the conformational change of this receptor at different activation stages.

Scientific Focus Area: Structural Biology

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