MAP kinase cascade signaling and endocytic trafficking: a marriage of convenience?
A hallmark of many signaling pathways is the spatial separation of activation and deactivation of signaling proteins. Quantitative analysis demonstrates that the spatial separation of a membrane-bound kinase and a cytosolic phosphatase potentially results in precipitous gradients of target phosphoproteins. Hypothetically, such gradients in the mitogen-activated protein kinase (MAPK) cascade would result in a strong attenuation of the phosphorylation signal towards the nucleus. When effective signal transduction is hampered by slow protein diffusion and rapid dephosphorylation, phosphoprotein trafficking within endocytic vesicles might be an efficient way to propagate the signals. Additional mechanisms facilitating information transfer could involve the assembly of MAP kinases on a scaffolding protein and active transport of signaling complexes by molecular motors. The proposed mechanism explains recent observations that MAPK activation can be strongly suppressed by various inhibitors of endocytosis.
Kholodenko
Boris N
BN
Dept of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA. Boris.Kholodenko@mail.tju.edu
D000818:Animals; D002451:Cell Compartmentation; D004705:Endocytosis / Q000502:physiology*; D006801:Humans; D020935:MAP Kinase Signaling System; D008870:Microtubules / Q000502:physiology; D021381:Protein Transport