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Original Article |
Correspondence to: Lukas A. Huber, Institute of Molecular Pathology, Dr. Bohr-Gasse 7, A-1030 Vienna, Austria. Tel:43-179-730-885 Fax:43-179-87-153 E-mail:huber{at}nt.imp.univie.ac.at.
We have identified a novel, highly conserved protein of 14 kD copurifying with late endosomes/lysosomes on density gradients. The protein, now termed p14, is peripherally associated with the cytoplasmic face of late endosomes/lysosomes in a variety of different cell types.
In a two-hybrid screen with p14 as a bait, we identified the mitogen-activated protein kinase (MAPK) scaffolding protein MAPK/extracellular signalregulated kinase (ERK) kinase (MEK) partner 1 (MP1) as an interacting protein. We confirmed the specificity of this interaction in vitro by glutathione S-transferase pull-down assays and by coimmunoprecipitation, cosedimentation on glycerol gradients, and colocalization. Moreover, expression of a plasma membranetargeted p14 causes mislocalization of coexpressed MP1. In addition, we could reconstitute protein complexes containing the p14MP1 complex associated with ERK and MEK in vitro.
The interaction between p14 and MP1 suggests a MAPK scaffolding activity localized to the cytoplasmic surface of late endosomes/lysosomes, thereby combining catalytic scaffolding and subcellular compartmentalization as means to modulate MAPK signaling within a cell.
Key Words: signal transduction scaffold, MEK, ERK, subcellular localization, endocytosis
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