MO25 is a master regulator of SPAK/OSR1 and MST3/MST4/YSK1 protein kinases

Beatrice M Filippi, Paola de los Heros, Youcef Mehellou, Iva Navratilova, Robert Gourlay, Maria Deak, Lorna Plater, Rachel Toth, Elton Zeqiraj, Dario R Alessi

Research output: Contribution to journalArticlepeer-review

89 Citations (Scopus)


Mouse protein-25 (MO25) isoforms bind to the STRAD pseudokinase and stabilise it in a conformation that can activate the LKB1 tumour suppressor kinase. We demonstrate that by binding to several STE20 family kinases, MO25 has roles beyond controlling LKB1. These new MO25 targets are SPAK/OSR1 kinases, regulators of ion homeostasis and blood pressure, and MST3/MST4/YSK1, involved in controlling development and morphogenesis. Our analyses suggest that MO25α and MO25β associate with these STE20 kinases in a similar manner to STRAD. MO25 isoforms induce approximately 100-fold activation of SPAK/OSR1 dramatically enhancing their ability to phosphorylate the ion cotransporters NKCC1, NKCC2 and NCC, leading to the identification of several new phosphorylation sites. siRNA-mediated reduction of expression of MO25 isoforms in mammalian cells inhibited phosphorylation of endogenous NKCC1 at residues phosphorylated by SPAK/OSR1, which is rescued by re-expression of MO25α. MO25α/β binding to MST3/MST4/YSK1 also stimulated kinase activity three- to four-fold. MO25 has evolved as a key regulator of a group of STE20 kinases and may represent an ancestral mechanism of regulating conformation of pseudokinases and activating catalytically competent protein kinases.
Original languageEnglish
Pages (from-to)1730-41
Number of pages12
JournalThe EMBO journal
Issue number9
Publication statusPublished - 4 May 2011


  • Animals
  • Calcium-Binding Proteins
  • Enzyme Activation
  • Escherichia coli
  • HEK293 Cells
  • Homeostasis
  • Humans
  • Immunoblotting
  • Insects
  • Intracellular Signaling Peptides and Proteins
  • Morphogenesis
  • Phosphorylation
  • Protein Isoforms
  • Protein-Serine-Threonine Kinases
  • RNA, Small Interfering
  • Transcription Factors


Dive into the research topics of 'MO25 is a master regulator of SPAK/OSR1 and MST3/MST4/YSK1 protein kinases'. Together they form a unique fingerprint.

Cite this