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Distinct roles of MK2 and MK5 in cAMP/PKA- and stress/p38MAPK-induced heat shock protein 27 phosphorylation.

Shiryaev A, Dumitriu G, Moens U - J Mol Signal (2011)

Bottom Line: Depletion of MK2, but not MK3 and MK5 diminished stress-induced HSP27 phosphorylation, while only knockdown of MK5 reduced PKA-induced phosphoHSP27 levels.Our results suggest that in HEK293 cells MK2 is the HSP27 kinase engaged in stress-induced, but not cAMP-induced phosphorylation of HSP27, while MK5 seems to be the sole MK to mediate HSP27 phosphorylation in response to stimulation of the PKA pathway.Thus, despite the same substrate specificity towards HSP27, MK2 and MK5 are implicated in different signaling pathways causing actin reorganization.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of Tromsø, Faculty of Health Sciences, Department of Medical Biology, Host-Microbe Interaction Research Group, N-9037 Tromsø, Norway. Ugo.Moens@uit.no.

ABSTRACT

Background: Classical mammalian mitogen-activated protein kinase (MAPK) pathways consist of a cascade of three successive phosphorylation events resulting in the phosphorylation of a variety of substrates, including another class of protein kinases referred to as MAPK-activating protein kinases (MAPKAPKs). The MAPKAPKs MK2, MK3 and MK5 are closely related, but MK2 and MK3 are the major downstream targets of the p38MAPK pathway, while MK5 can be activated by the atypical MAPK ERK3 and ERK4, protein kinase A (PKA), and maybe p38MAPK. MK2, MK3, and MK5 can phosphorylate the common substrate small heat shock protein 27 (HSP27), a modification that regulates the role of HSP27 in actin polymerization. Both stress and cAMP elevating stimuli can cause F-actin remodeling, but whereas the in vivo role of p38MAPK-MK2 in stress-triggered HSP27 phosphorylation and actin reorganization is well established, it is not known whether MK2 is involved in cAMP/PKA-induced F-actin rearrangements. On the other hand, MK5 can phosphorylate HSP27 and cause cytoskeletal changes in a cAMP/PKA-dependent manner, but its role as HSP27 kinase in stress-induced F-actin remodeling is disputed. Therefore, we wanted to investigate the implication of MK2 and MK5 in stress- and PKA-induced HSP27 phosphorylation.

Results: Using HEK293 cells, we show that MK2, MK3, and MK5 are expressed in these cells, but MK3 protein levels are very moderate. Stress- and cAMP-elevating stimuli, as well as ectopic expression of active MKK6 plus p38MAPK or the catalytic subunit of PKA trigger HSP27 phosphorylation, and specific inhibitors of p38MAPK and PKA prevent this phosphorylation. Depletion of MK2, but not MK3 and MK5 diminished stress-induced HSP27 phosphorylation, while only knockdown of MK5 reduced PKA-induced phosphoHSP27 levels. Stimulation of the p38MAPK, but not the PKA pathway, caused activation of MK2.

Conclusion: Our results suggest that in HEK293 cells MK2 is the HSP27 kinase engaged in stress-induced, but not cAMP-induced phosphorylation of HSP27, while MK5 seems to be the sole MK to mediate HSP27 phosphorylation in response to stimulation of the PKA pathway. Thus, despite the same substrate specificity towards HSP27, MK2 and MK5 are implicated in different signaling pathways causing actin reorganization.

No MeSH data available.


Related in: MedlinePlus

Different stimuli that trigger HSP27 phosphorylation engage distinct pathways with specific MKs. MK2 mediates phosphorylation of HSP27 in cells with an activated p38MAPK pathway, while MK5 functions as an HSP27 kinase induced by the cAMP/PKA pathway.
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Figure 5: Different stimuli that trigger HSP27 phosphorylation engage distinct pathways with specific MKs. MK2 mediates phosphorylation of HSP27 in cells with an activated p38MAPK pathway, while MK5 functions as an HSP27 kinase induced by the cAMP/PKA pathway.

Mentions: In conclusion, we suggest that both MK2 and MK5 are genuine HSP27 kinases that are engaged in different pathways. While MK2 mediates phosphorylation of HSP27 in response to stress-induced activation of the p38MAPK pathway, MK5 seems to be involved in phosphorylation of HSP27 triggered by PKA (Figure 5). Aberrant HSP27 phosphorylation levels have been observed during viral infections, in diabetic kidney and heart, and in diseases such as cancer, the autoimmune diseases pemphigus vulgaris and pemphigus foliaceus, and kidney fibrosis [14]. Hence, meticulous mapping of the different pathways and protein kinases involved in perturbed HSP27 phosphorylation in these clinical conditions may allow the design of specific therapeutic approaches to prevent abnormal phosphoHSP27 levels.


Distinct roles of MK2 and MK5 in cAMP/PKA- and stress/p38MAPK-induced heat shock protein 27 phosphorylation.

Shiryaev A, Dumitriu G, Moens U - J Mol Signal (2011)

Different stimuli that trigger HSP27 phosphorylation engage distinct pathways with specific MKs. MK2 mediates phosphorylation of HSP27 in cells with an activated p38MAPK pathway, while MK5 functions as an HSP27 kinase induced by the cAMP/PKA pathway.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3117753&req=5

Figure 5: Different stimuli that trigger HSP27 phosphorylation engage distinct pathways with specific MKs. MK2 mediates phosphorylation of HSP27 in cells with an activated p38MAPK pathway, while MK5 functions as an HSP27 kinase induced by the cAMP/PKA pathway.
Mentions: In conclusion, we suggest that both MK2 and MK5 are genuine HSP27 kinases that are engaged in different pathways. While MK2 mediates phosphorylation of HSP27 in response to stress-induced activation of the p38MAPK pathway, MK5 seems to be involved in phosphorylation of HSP27 triggered by PKA (Figure 5). Aberrant HSP27 phosphorylation levels have been observed during viral infections, in diabetic kidney and heart, and in diseases such as cancer, the autoimmune diseases pemphigus vulgaris and pemphigus foliaceus, and kidney fibrosis [14]. Hence, meticulous mapping of the different pathways and protein kinases involved in perturbed HSP27 phosphorylation in these clinical conditions may allow the design of specific therapeutic approaches to prevent abnormal phosphoHSP27 levels.

Bottom Line: Depletion of MK2, but not MK3 and MK5 diminished stress-induced HSP27 phosphorylation, while only knockdown of MK5 reduced PKA-induced phosphoHSP27 levels.Our results suggest that in HEK293 cells MK2 is the HSP27 kinase engaged in stress-induced, but not cAMP-induced phosphorylation of HSP27, while MK5 seems to be the sole MK to mediate HSP27 phosphorylation in response to stimulation of the PKA pathway.Thus, despite the same substrate specificity towards HSP27, MK2 and MK5 are implicated in different signaling pathways causing actin reorganization.

View Article: PubMed Central - HTML - PubMed

Affiliation: University of Tromsø, Faculty of Health Sciences, Department of Medical Biology, Host-Microbe Interaction Research Group, N-9037 Tromsø, Norway. Ugo.Moens@uit.no.

ABSTRACT

Background: Classical mammalian mitogen-activated protein kinase (MAPK) pathways consist of a cascade of three successive phosphorylation events resulting in the phosphorylation of a variety of substrates, including another class of protein kinases referred to as MAPK-activating protein kinases (MAPKAPKs). The MAPKAPKs MK2, MK3 and MK5 are closely related, but MK2 and MK3 are the major downstream targets of the p38MAPK pathway, while MK5 can be activated by the atypical MAPK ERK3 and ERK4, protein kinase A (PKA), and maybe p38MAPK. MK2, MK3, and MK5 can phosphorylate the common substrate small heat shock protein 27 (HSP27), a modification that regulates the role of HSP27 in actin polymerization. Both stress and cAMP elevating stimuli can cause F-actin remodeling, but whereas the in vivo role of p38MAPK-MK2 in stress-triggered HSP27 phosphorylation and actin reorganization is well established, it is not known whether MK2 is involved in cAMP/PKA-induced F-actin rearrangements. On the other hand, MK5 can phosphorylate HSP27 and cause cytoskeletal changes in a cAMP/PKA-dependent manner, but its role as HSP27 kinase in stress-induced F-actin remodeling is disputed. Therefore, we wanted to investigate the implication of MK2 and MK5 in stress- and PKA-induced HSP27 phosphorylation.

Results: Using HEK293 cells, we show that MK2, MK3, and MK5 are expressed in these cells, but MK3 protein levels are very moderate. Stress- and cAMP-elevating stimuli, as well as ectopic expression of active MKK6 plus p38MAPK or the catalytic subunit of PKA trigger HSP27 phosphorylation, and specific inhibitors of p38MAPK and PKA prevent this phosphorylation. Depletion of MK2, but not MK3 and MK5 diminished stress-induced HSP27 phosphorylation, while only knockdown of MK5 reduced PKA-induced phosphoHSP27 levels. Stimulation of the p38MAPK, but not the PKA pathway, caused activation of MK2.

Conclusion: Our results suggest that in HEK293 cells MK2 is the HSP27 kinase engaged in stress-induced, but not cAMP-induced phosphorylation of HSP27, while MK5 seems to be the sole MK to mediate HSP27 phosphorylation in response to stimulation of the PKA pathway. Thus, despite the same substrate specificity towards HSP27, MK2 and MK5 are implicated in different signaling pathways causing actin reorganization.

No MeSH data available.


Related in: MedlinePlus