Co-immunoprecipitation (Co-IP) of G Protein-Coupled Receptor (GPCR)-Receptor Tyrosine Kinase (RTK) Complexes from the Dorsal Hippocampus of the Rat Brain

A large body of evidence indicates that G protein-coupled receptors (GPCRs) and receptor tyrosine kinases (RTKs) can form heteroreceptor complexes. In these complexes, the signaling from each interacting protomer is modulated to produce an integrated and therefore novel response upon agonist(s) activation. In the GPCR-RTK heteroreceptor complexes, GPCRs can activate RTK in the absence of added growth factor through the use of RTK signaling molecules. This integrative phenomenon is reciprocal and can place also RTK signaling downstream of GPCR. The existence of either stable or transient GPCR-RTK homo- and heteroreceptor complexes with allosteric receptor-receptor interactions increases the diversity of receptor function including recognition, trafficking, and signaling. The isolation and characterization of GPCR-RTK heteroreceptor complexes are therefore important to understand these processes. Co-immunoprecipitation (Co-IP) is a straightforward technique to study in vivo GPCR-RTK interactions and can identify interacting proteins or heteroreceptor complexes present in cell extracts. Here, we present detailed protocol for Co-IP of GPCR-RTK heteroreceptor complexes from brain membrane preparations using as an example the study of A2AR-TrkB heteroreceptor complexes in the rat dorsal hippocampus.