Characterization of the protein interaction profile of the human kinase Nek4 and assignment of its functional context

Author(s)

Fernanda Luisa Basei

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
• Defense date: 2014-06-27

Examining board members

Jörg Kobarg; Alessandra Luiza Pelegrini; Ana Carolina de Mattos Zeri; Juliana Helena Costa Smetana; Nadja Cristhina de Souza Pinto

• Advisor: Jörg Kobarg

Abstract

Neks are serine-threonine kinases that are similar to NIMA, a protein found in Aspergillus nidulans which is essential for cell division. In humans there are eleven Neks (1-11) which are involved in different biological functions besides the cell cycle control. Nek4 is one of largest members of the Neks family and has been related to the primary cilia formation and in DNA damage response. However, its substrates and interaction partners are still unknown. Thus in an attempt to better understand the role of Nek4 we performed an interactomics study to find new biological processes in which Nek4 is involved. Besides, we described here a novel Nek4 isoform and compared the interactomics profile of these two Nek4 proteins. Isoform 1 and isoform 2 of Nek4 were expressed in human cells and after an immunoprecipitation followed by mass spectrometry, 474 interacting proteins were identified for isoform 1 and 149 for isoform 2 of Nek4. 102 proteins are common interactors between both isoforms. Our results confirm Nek4 involvement in the DNA damage response, cilia maintenance and microtubules stabilization, and raise the possibility of new functional contexts including mRNA processing, apoptosis signaling, stress response, translation and protein quality control. Among the interaction partners, we found important proteins such as TRAP-1, Whirlin, PCNA, 14-3-3?, Btf, PARP-1, SRSF1, PAI-RBP1 and KAP-1. We could observe that both isoforms share functions that are new to the Nek family, and isoform 1 apparently has also maintained functions which have already been established to other Nek family members. From our immunoprecipitation followed by mass spectrometry experiment a possible site for Nek4 autophosphorylation and dimerization was identified. This study provides new insights into Nek4 functions, identifying new interaction partners, localization to new cellular compartment and further suggests an interesting difference between isoform 1 and the novel isoform 2 of Nek4. Nek4 isoform 1 may have maintained similar roles compared to other Neks and these roles are not related to isoform 2 (AU)

• FAPESP's process: 09/14221-3 - Characterization of the two human signaling proteins Nek 11 and Nek 4 - a biochemical and functional approach
• Grantee: Fernanda Luisa Basei
• Support Opportunities: Scholarships in Brazil - Doctorate