Interaction of the N-methyl-D-aspartic acid receptor NR2D subunit with thec-Abl tyrosine kinase

The COOH-terminal domain of the NR2D subunit of the NMDA receptor contains proline-rich regions that show striking homology to sequences known to bind to Src homology 3 (SH3) domains. To determine whether the proline-rich reg ion of the NR2D subunit interacts with specific SH3 domains, in vitro SH3 d omain binding assays were performed. A proline-rich fragment of the NR2D su bunit (2D(866-1064)) bound to the Abl SH3 domain but not to the SH3 domains from Src, Fyn, Grb2, GAP, or phospholipase C-gamma (PLC gamma). Co-immunop recipitation of NR2D with Abl suggests stable association of NR2D and Abl i n transfected cells. The SH3 domain plays an important role in the negative regulation of Abl kinase activity. To determine whether the interaction of NR2D with the Abl SH3 domain alters Abl kinase activity, Abl was expressed alone or with NR2D in 293T cells. Autophosphorylation of Abl was readily o bserved when Abl was expressed alone. However, co-expression of Abl with 2D (866-1064) or full-length NR2D inhibited autophosphorylation. 2D(866-1064) did not inhibit Delta SH3 Abl, indicating a requirement for the Abl SH3 dom ain in the inhibitory effect, Similarly, 2D(866-1064) did not inhibit the c atalytic activity of Abl-PP, which contains two point mutations in the SH2- kinase linker domain that release the negative kinase regulation by the SH3 domain. In contrast, the full-length NR2D subunit partially inhibited the autokinase activity of both Delta SH3 Abl and Abl-PP, suggesting that NR2D and Abl may interact at multiple sites. Taken together, the data in this re port provide the first evidence for a novel inhibitory interaction between the NR2D subunit of the MMDA receptor and the Abl tyrosine kinase.