SUMOylation Is Required for ERK5 Nuclear Translocation and ERK5-Mediated Cancer Cell Proliferation.

Tatiana Erazo,Néstor Gómez,Jose M Lizcano,Nora Diéguez-Martínez,Sergio Espinosa-Gil

doi:10.3390/ijms21062203

Tatiana Erazo, Néstor Gómez + Show 3 more

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https://doi.org/10.3390/ijms21062203

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Abstract

The MAP kinase ERK5 contains an N-terminal kinase domain and a unique C-terminal tail including a nuclear localization signal and a transcriptional activation domain. ERK5 is activated in response to growth factors and stresses and regulates transcription at the nucleus by either phosphorylation or interaction with transcription factors. MEK5-ERK5 pathway plays an important role regulating cancer cell proliferation and survival. Therefore, it is important to define the precise molecular mechanisms implicated in ERK5 nucleo-cytoplasmic shuttling. We previously described that the molecular chaperone Hsp90 stabilizes and anchors ERK5 at the cytosol and that ERK5 nuclear shuttling requires Hsp90 dissociation. Here, we show that MEK5 or overexpression of Cdc37—mechanisms that increase nuclear ERK5—induced ERK5 Small Ubiquitin-related Modifier (SUMO)-2 modification at residues Lys6/Lys22 in cancer cells. Furthermore, mutation of these SUMO sites abolished the ability of ERK5 to translocate to the nucleus and to promote prostatic cancer PC-3 cell proliferation. We also show that overexpression of the SUMO protease SENP2 completely abolished endogenous ERK5 nuclear localization in response to epidermal growth factor (EGF) stimulation. These results allow us to propose a more precise mechanism: in response to MEK5 activation, ERK5 SUMOylation favors the dissociation of Hsp90 from the complex, allowing ERK5 nuclear shuttling and activation of the transcription.

Highlights

The extracellular-signal-regulated kinase 5 (ERK5, called Big MAP Kinase-1 (BMK1)) is the most structurally divergent member of the mitogen-activated protein kinase (MAPK) family
To investigate whether Small Ubiquitin-related Modifier (SUMO) modification is required for ERK5 nuclear translocation, we performed in vivo SUMOylation assays
We transiently overexpressed in HEK293T cells SUMO2, the E2-conjugating enzyme Ubc9 and FLAG-tagged ERK5, in combination with a constitutive active form of MEK5

Summary

Introduction

The extracellular-signal-regulated kinase 5 (ERK5, called Big MAP Kinase-1 (BMK1)) is the most structurally divergent member of the mitogen-activated protein kinase (MAPK) family. ERK5 activates transcription by either phosphorylation of transcription factors such as MEF2 [3], Sap1 [4] or c-Myc [5,6] or through the TAD domain in a kinase-independent mechanism. ERK5 is ubiquitously expressed in numerous tissues and is activated in response to growth factors and to different forms of stress. MEK5 is the only upstream kinase described for ERK5, and, MEK5-ERK5 constitutes a unique signaling axis to control cell differentiation, proliferation and survival [8]. Active ERK5 phosphorylates and activates MEF2A, C and D transcription factors [3,5,16], promoting c-Junand c-Fos-mediated expressions of cyclin D1 required for cell proliferation [4,17]. ERK5 allows cancer cells to evade cell cycle suppressors by impairing the expression of the CDK inhibitors p15, p21 and p27 [18,19]

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