The P38/MAPK Pathway Regulates Microtubule Polymerization Through Phosphorylation Of MAP4 And Op18 In Hypoxic Cells

Rationale: In both cardiomyocytes and HeLa cells, hypoxia (1% O2, in 15 min) leads to microtubule disruption quickly, but little is known about how the microtubules dynamics change at the early hypoxia stage.Objective: We wonder whether hypoxia-activated p38Mitogen-activated protein kinase (p38/MAPK) is tightly connected with microtubule disruption, and how it induces the changes.Methods and Results: First, we examine the two microtubule regulators activity: microtubule associated protein 4 (MAP4) activity decreases while the oncoprotein 18/stathmin (Op18) activity increases after hypoxia, but their protein levels do not change, and the p38/MAPK activity increases quickly after hypoxia and has the same peak as the MAP4 activity. We then use the p38/MAPK inhibitor SB203580 and a constitutively activated p38/MAPK activator, MKK6 (Glu), to observe the effect of p38/MAPK on MAP4 and Op18. This activated p38/MAPK signaling leads to MAP4 phosphorylation and inactivation, and it makes Op18 dephosphorylation and activation, both of which induce microtubule disruption. Next, we confirm the interaction between phospho-p38 and MAP4 using immunoprecipitation and immunofluorescence. At last, we test the cell viability, and find that the SB203580 protect the hypoxic cells and the MKK6 (Glu) overexpression makes the cell viability decrease.Conclusion: Our results demonstrate that hypoxia induces microtubule depolymerizaion via activation of p38/MAPK signaling pathway and its downstream effectors MAP4 and Op18 phosphorylation levels. This kinase and the two regulators contr ol cell viability via regulation of microtubule dynamics.