Biopolymers and cell. 2005; 21 (1): 48 - 54

Intra- and intermolecular interactions mediated by adaptor protein Ruk/CIN85/SETA

O. M. Ilnytska, V. R. Drel', H. Yu. Shuvayeva, S. V. Havrylov, Ya. Ya. Fedyshyn, O. M. Mayevska, N. I. Ihumentseva, I. T. Gout, V. L. Buchman, L. B. Drobot

Ruk/CIN85/SETA is a member of a separate and evolutionary conserved family of adapter/scaffold proteins implicated in apoptic and receptor tyrosine kinases signalling, rearrangement of actin cytoskeleton and cell adhesion, podocyte and T cell functions. Self-regulation through intra- and intercellular interactions can be supposed for Ruk/CIN85/SETA as this protein contains SH3 domains and proline-rich sequence, localized within one polypeptide chain, as well as C-terminal coiled-coil region. The ability of Ruk proline-rich motifs to interact with its own SH3 domains in an intramolecular fashion and coiled-coil region to mediate oligomerization between different isoforms was assessed in GST pull down experiments. It was shown that both Ruk SH3A and to a less extent SH3B domains can interact with its own proline-rich sequences in a cooperative manner, while coiled-coil region provide for isoforms oligomerization. SH3C domain appear exerts conformational constraints, imposed on coiled-coil region, restricting the level of oligomerization. We also demonstrated that the ability of exogenous ligands to interact with Ruk polyproline motifs is changing during the course of TNFa-induced apoptosis of human myelomonocytic U937 cells.

Key words: adaptor protein, SH3 domain, proline-rich region, coiled-coil region, protein-protein interaction.