Presentation: Mapping the Sequence of the Human Tpl2 to a Structural Model: Implications to Signaling Defects (2007)

848 Mapping the Sequence of the Human Tpl2 to a Structural Model: Implications to Signaling Defects

Background: Tpl2, a serine-threonine protein kinase, encoded by the Tpl2 protooncogene plays a critical role in both innate and adaptive immunity regulating diverse responses to inflammatory stimuli. It has been shown that NF-κB suppression is beneficial in many models of inflammatory and autoimmune diseases. Sequence analysis has revealed 3 functional domains for Tpl2. The N-terminal domain, which shows low homology to protein kinases, the central domain that is similar to known MAPK domains, and the C-terminal active loop that relates to NF-κB binding. The 3-D structure of the Tpl2 protein was not known upon now.
Purpose: a) To recognize the different functional domains of Tpl2; b) To locate functional residues (i.e. phosphorylation sites) on the 3-D models; and c) To identify regions of functional importance as well as regions that are involved in signaling defects.
Methods: Sequences were aligned using the ClustalX and T-Coffee programs. 3-D model structures of the Tpl2 were created with MODELLER and the Swiss-model automated protein structure homology-modeling server, by using various protein structures as templates. The derived model was checked for folding and packing errors.
Results: The N-terminal domain of Tpl2 is being modeled to its homologous 1APM and ATP-dependent phosphoenolpyruvate carboxykinase, phosphorylation N-terminus. The middle domain has been extensively modeled, based on several kinase structures with high homology (2CLQ, 2C30, 1DAN, 1F3M, 1TK1, 2PHK). The activation site, the central functional region of the whole structure, is characterized by phosphorylation sites. The C-terminal domain, known to be associated with the binding of NF-κB1, has been placed on the 3D model with respect to the binding site.
Conclusions: The N-terminal domain of Tpl2, with low sequence homology to the ATP-dependent phosphoenolpyruvate carboxykinase, possesses an amphipathic α-helix and carries a phosphorylation site at the amino acid residue Thr62. More information dealing with the putative implications of the middle domain of Tpl2 in signalling pathways could be provided by a better understanding of the structure of this domain. The C-terminus contains candidate autophosphorylation sites that might act as recognition sites for the NF-κB domains. The impact of the assembled model may reflect to the design of proper site-directed mutagenesis experiments, in order to study and learn more about the signaling pathways Tpl2 is implicated in and it could also reveal new strategies for more effective pharmacological inhibition.

 E. Eliopoulos, None; I. Kyrmizi, None; D.T. Boumpas, None; G.N. Goulielmos, None.