Interaction between very-KIND Ras guanine exchange factor and microtubule-associated protein 2, and its role in dendrite growth--structure and function of the second kinase noncatalytic C-lobe domain.

The kinase noncatalytic C-lobe domain (KIND) is a putative protein-protein interaction module. Four KIND-containing proteins, Spir-2 (actin-nuclear factor), PTPN13 (protein tyrosine phosphatase), FRMPD2 (scaffold protein) and very-KIND (v-KIND) (brain-specific Ras guanine nucleotide exchange factor), have been identified to date. Uniquely, v-KIND has two KINDs (i.e. KIND1 and KIND2), whereas the other three proteins have only one. The functional role of KIND, however, remains unclear. We previously demonstrated that v-KIND interacts with the high-molecular weight microtubule-associated protein 2 (MAP2), a dendritic microtubule-associated protein, leading to negative regulation of neuronal dendrite growth. In the present study, we analyzed the structure-function relationships of the v-KIND-MAP2 interaction by generating a series of mutant constructs. The interaction with endogenous MAP2 in mouse cerebellar granule cells was specific to v-KIND KIND2, but not KIND1, and was not observed for the KINDs from other KIND-containing proteins. The binding core modules critical for the v-KIND-MAP2 interaction were defined within 32 residues of the mouse v-KIND KIND2 and 43 residues of the mouse MAP2 central domain. Three Leu residues at amino acid positions 461, 474 and 477 in the MAP2-binding core module of KIND2 contributed to the interaction. The MAP2-binding core module itself promoted dendrite branching as a dominant-negative regulator of v-KIND in hippocampal neurons. The results reported in the present study demonstrate the structural and functional determinant underlying the v-KIND-MAP2 interaction that controls dendrite arborization patterns.