 In ApoER2, there is a proline-rich 59 amino acid insert encoded by the alternatively spliced exon 19.This insert allows for protein interactions that are unable to occur with other LDL receptors.It binds the PSD-95 adapter protein, cross-linking ApoER2 and the NMDA receptors during the process of long-term potentiation, and is also bound specifically by JIP-2, an important interaction in the JNK signalling pathway.