Erk5 inhibits endothelial migration via KLF2-dependent down-regulation of PAK1.
OBJECTIVE
The MEK5/Erk5 pathway mediates beneficial effects of laminar flow, a major physiological factor preventing vascular dysfunction. Forced Erk5 activation induces a protective phenotype in endothelial cell (EC) that is associated with a dramatically decreased migration capacity of those cells. Transcriptional profiling identified the Krüppel-like transcription factors KLF2 and KLF4 as central mediators of Erk5-dependent gene expression. However, their downstream role regarding migration is unclear and relevant secondary effectors remain elusive. Here, we further investigated the mechanism underlying Erk5-dependent migration arrest in ECs.


RESULTS
Our experiments reveal KLF2-dependent loss of the pro-migratory Rac/Cdc42 mediator, p21-activated kinase 1 (PAK1), as an important mechanism of Erk5-induced migration inhibition. We show that endothelial Erk5 activation by expression of a constitutively active MEK5 mutant, by statin treatment, or by application of laminar shear stress strongly decreased PAK1 mRNA and protein expression. Knockdown of KLF2 but not of KLF4 prevented Erk5-mediated PAK1 mRNA inhibition, revealing KLF2 as a novel PAK1 repressor in ECs. Importantly, both PAK1 re-expression and KLF2 knockdown restored the migration capacity of Erk5-activated ECs underscoring their functional relevance downstream of Erk5.


CONCLUSIONS
Our data provide first evidence for existence of a previously unknown Erk5/KLF2/PAK1 axis, which may limit undesired cell migration in unperturbed endothelium and lower its sensitivity for migratory cues that promote vascular diseases including atherosclerosis.
Department of Dermatology, University Hospital Würzburg, Josef-Schneider-Straße 2, Würzburg 97080, Germany.
Ravi K
RK
Komaravolu
Department of Dermatology, University Hospital Würzburg, Josef-Schneider-Straße 2, Würzburg 97080, Germany.
Christian
C
Adam
Department of Pathology and Medical Biology, Cardiovascular Regenerative Medicine Research Group, University Medical Center Groningen, Groningen, Netherlands.
Jan-Renier A J
JR
Moonen
Department of Pathology and Medical Biology, Cardiovascular Regenerative Medicine Research Group, University Medical Center Groningen, Groningen, Netherlands.
Martin C
MC
Harmsen
Department of Dermatology, University Hospital Würzburg, Josef-Schneider-Straße 2, Würzburg 97080, Germany.
Matthias
M
Goebeler
Department of Dermatology, University Hospital Würzburg, Josef-Schneider-Straße 2, Würzburg 97080, Germany schmidt_M11@ukw.de.
Marc
M
Schmidt
D050197:Atherosclerosis / Q000209:etiology; D002465:Cell Movement / Q000235:genetics / Q000502:physiology*; D015536:Down-Regulation; D042783:Endothelial Cells / Q000378:metabolism / Q000502:physiology*; D055785:Gene Knockdown Techniques; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048671:MAP Kinase Kinase 5 / Q000235:genetics / Q000378:metabolism; D048054:Mitogen-Activated Protein Kinase 7 / Q000235:genetics / Q000378:metabolism*; D008955:Models, Cardiovascular; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*
C096161:KLF2 protein, human; C000715467:KLF4 protein, human; D000090062:Kruppel-Like Factor 4; D051741:Kruppel-Like Transcription Factors; D012333:RNA, Messenger; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D048054:Mitogen-Activated Protein Kinase 7; D048671:MAP Kinase Kinase 5; C482563:MAP2K5 protein, human
Endothelial migration; Erk5; Krüppel-like factor; Laminar shear stress; PAK1