The p38/MAPK pathway regulates microtubule polymerization through phosphorylation of MAP4 and Op18 in hypoxic cells

Abstract

In both cardiomyocytes and HeLa cells, hypoxia (1% O(2)) quickly leads to microtubule disruption, but little is known about how microtubule dynamics change during the early stages of hypoxia. We demonstrate that microtubule associated protein 4 (MAP4) phosphorylation increases while oncoprotein 18/stathmin (Op18) phosphorylation decreases after hypoxia, but their protein levels do not change. p38/MAPK activity increases quickly after hypoxia concomitant with MAP4 phosphorylation, and the activated p38/MAPK signaling leads to MAP4 phosphorylation and to Op18 dephosphorylation, both of which induce microtubule disruption. We confirmed the interaction between phospho-p38 and MAP4 using immunoprecipitation and found that SB203580, a p38/MAPK inhibitor, increases and MKK6(Glu) overexpression decreases hypoxic cell viability. Our results demonstrate that hypoxia induces microtubule depolymerization and decreased cell viability via the activation of the p38/MAPK signaling pathway and changes the phosphorylation levels of its downstream effectors, MAP4 and Op18.

Phosphorylation of DYNLT1 at Serine 82 Regulates Microtubule Stability and Mitochondrial Permeabilization in Hypoxia

“…It is known that Hypoxia treatment could reduce cell viability (Hu et al, 2010). We found that S82A improved the survival of hypoxic cells whereas S82E sharply reduced cell viability in hypoxia conditions.…”

“…This process is critical for the apical delivery of membrane cargoes and S82 phosphorylation leads to a reduced affinity for the dynein intermediate chain (Yeh et al, 2006). Since the above mentioned reports indicated a key role of DYNLT1 in modulating mPT and MT network stability, we hypothesized that phosphorylation of DYNLT1, especially on S82, might occur in hypoxia, based on our previous work in which we showed that hypoxia-activated p38/MAPK signaling pathway initiates MT disruption and alters cell viability by phosphorylating the downstream effector (Hu et al, 2010). In order to generalize these observations, we chose H9c2 and HeLa cells (Brito and Rieder, 2009;Wan et al, 2009) to study hypoxiareduced MTs disruption and mitochondrial permeabilization related to S82.…”

“…Our previous study showed that hypoxiainduced MAP4 phosphorylation leads to MT network disruption and an increase in free tubulin. Subsequently we demonstrated that MAP4 could alleviate MTs disruption and stabilize mitochondrial permeability transition (mPT) in hypoxia via dynein light chain Tctex-type 1 (DYNLT1) modulation (Fang et al, 2011;Hu et al, 2010). DYNLT1, widely expressed in a number of tissues in various species and a component of dynein complex, fulfills cargo binding function (Belmont and Mitchison, 1996;Chuang et al, 2001), and plays a key role in multiple processes including endomembrane organization, trafficking, mitosis, and MT organization (Nagano et al, 1998;Palmer et al, 2011).…”

Relevant coexpression of STMN1, MELK and FOXM1 in glioblastoma and review of the impact of STMN1 in cancer biology

“…4 Also in the MAPK cascade, apoptosis signal-regulating kinase (ASK1) activates the JNK and p38 MAPK cascades through STNM1 phosphorylation and ASK1 is involved in a broad range of activities including cell differentiation and stress-induced apoptosis. [45][46][47][48] Moreover, ribosomal protein S6 kinase A3 (RPS6KA3, RSK2) can reduce microtubule depolymerization by phosphorylation of STMN1 specifically at Ser16 residue. 49 Additionally, peptide hormones as gonadotropin--releasing hormone (LHRH) secreted from hypothalamic neurons, regulators of LH and FSH synthesis and release, have also been described to induce STMN1 phosphorylation in a PKC-dependent pathway.…”

Cardiac Function and Organ Blood Flow at Early Stage Following Severe Burn

“…Zhang et al also found that p38/MAPK involved in burn-induced degradation of myocardial cell membrane phospholipids, and revealed that it achieved such effects by adjusting cytosolic phospholipase A2 (cPLA2) (Zhang et al, 2007b). Moreover, hypoxia was recently found to cause myocardial cell microtubule depolymerization through activation of p38/MAPK and change of phosphorylation level of microtubule associated protein 4 (MAP4) and oncoprotein 18/stathmin (Op18) (Hu et al, 2009). Additionally, through F-actin cytoskeleton rearrangement and phosphorylation of L-caldesmon, p38/MAPK conducted an important role in endothelial barrier dysfunction induced by burn serum (Chu et al, 2010).…”