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Mortalin-MPD (mevalonate pyrophosphate decarboxylase) interactions and their role in control of cellular
Renu Wadhwa1, Tomoko Yaguchi, Md Kamrul Hasan
1National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8566, Japan.
Abstract:
Mortalin (mot-2/GRP75/PBP74/mthsp70) is a member of the hsp70 family of proteins and is differentially distributed in normal and immortal cells. It was shown to be involved in pathways to cell senescence and immortalization. To elucidate its functional aspects, a yeast interactive screen for mortalin (mot-2) binding proteins was performed. Mevalonate pyrophosphate decarboxylase (MPD) was identified as one of the mortalin binding partners. The interactions were confirmed in mammalian cells by two-hybrid assay and in vivo coimmunoprecipitation. MPD is known to furnish prenyl groups required for prenylation, protein modification that is essential for the activity of many proteins including p21(Ras) (Ras). We have examined the effect of MPD-mot-2 interactions on the level and activity of p21(Ras) and its downstream effectors, p44 and p42 MAP kinases (ERK1/ERK2), in Ras-Raf pathway. An overexpression of mot-2 resulted in reduced level of Ras and phosphorylated ERK2. These were rescued by co-expression of MPD from an exogenous promoter demonstrating a functional link between mot-2, MPD, and Ras. Ras and its oncogenic forms act as key players in controlling proliferation of normal and cancerous cells. Assigning mot-2 upstream of p21(Ras) offers an important mechanism for influence over cell proliferation.
Insights
Mortalin (mot-2) interacts with mevalonate pyrophosphate decarboxylase (MPD), influencing the Ras-Raf pathway. This interaction affects cell proliferation by modulating p21(Ras) levels and activity.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Mortalin (mot-2), a heat shock protein 70 family member, is implicated in cell senescence and immortalization.
- Differential distribution of mortalin in normal and immortal cells suggests a role in cell fate regulation.
- The Ras-Raf pathway is crucial for controlling normal and cancerous cell proliferation.
Purpose of the Study:
- To identify mortalin-binding proteins and elucidate mortalin's functional role in cell proliferation.
- To investigate the interaction between mortalin and mevalonate pyrophosphate decarboxylase (MPD).
- To determine the impact of the mortalin-MPD interaction on the Ras-Raf pathway.
Main Methods:
- Yeast interactive screen to identify mortalin-binding proteins.
- Confirmation of interactions in mammalian cells using two-hybrid assays and co-immunoprecipitation.
- Analysis of p21(Ras) levels, activity, and downstream MAP kinase (ERK1/ERK2) phosphorylation.
Main Results:
- Mevalonate pyrophosphate decarboxylase (MPD) was identified as a mortalin-binding partner.
- Overexpression of mortalin reduced p21(Ras) levels and ERK1/ERK2 phosphorylation.
- Co-expression of MPD rescued these effects, demonstrating a functional link between mortalin, MPD, and Ras.
Conclusions:
- Mortalin interacts with MPD, a key enzyme in prenylation.
- This interaction influences the Ras-Raf pathway, impacting cell proliferation.
- Mortalin acts upstream of p21(Ras), providing a mechanism to control cell proliferation.