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Mitochondrial ChChD3 acts as a Scaffold for Mitofilin, Sam50 and PKA
Author(s) -
Darshi Manjula,
Taylor Susan S
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.645.20
Subject(s) - immunoprecipitation , mitochondrion , protein subunit , microbiology and biotechnology , hek 293 cells , phosphorylation , protein kinase a , biology , scaffold protein , nucleus , chemistry , biochemistry , signal transduction , receptor , gene
Cyclic AMP dependent protein kinase A (PKA) is ubiquitous in mammalian cells and plays a critical role in the regulation of various cellular processes. Thus, it has many substrates which usually are highly tissue specific. ChChd3 is one such substrate which we have recently identified by using analog sensitive catalytic subunit of PKA. ChChd3 contains a myristylation motif followed by DUF domain and a CHCH domain. In mouse fibroblasts, the endogenous ChChd3 is primarily localized to mitochondria, sometimes also seen in nucleus. However, over‐expressed ChChd3 is localized only to mitochondria. Deletion of CHCH domain disrupts mitochondrial localization suggesting that CHCH domain is an essential targeting motif in ChChd3. In vitro protein import studies showed that in addition to cysteines in CHCH domain, myristoylation is also necessary for targeting the protein to the IM of mitochondria. Over‐expressed ChChd3 in HEK 293 cells binds to PKA and shows a clear increase in phosphorylation at Thr10 upon stimulation with 8‐CPT cAMP. Further, immunofluorescence and sub‐cellular fractionation studies showed that the protein is phosphorylated in mitochondria and translocated to nucleus. Co‐immunoprecipitation of mitochondrial proteins, Mitofilin and Sam50 with ChChd3 suggests that ChChd3 may be involved in protein import along with Sam50. Studies are currently underway to see the role of ChChd3 as part of mitochondrial protein import machinery.