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SnRK1 from Arabidopsis thaliana is an atypical AMPK
Author(s) -
Emanuelle Shane,
Hossain Mohammed Iqbal,
Moller Isabel E.,
Pedersen Henriette L.,
Meene Allison M. L.,
Doblin Monika S.,
Koay Ann,
Oakhill Jonathan S.,
Scott John W.,
Willats William G. T.,
Kemp Bruce E.,
Bacic Antony,
Gooley Paul R.,
Stapleton David I.
Publication year - 2015
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/tpj.12813
Subject(s) - protein subunit , heterotrimeric g protein , arabidopsis thaliana , arabidopsis , biology , biochemistry , protein kinase a , dephosphorylation , immunoprecipitation , gene isoform , microbiology and biotechnology , phosphorylation , mutant , phosphatase , signal transduction , gene , g protein
Summary SNF1‐related protein kinase 1 (SnRK1) is the plant orthologue of the evolutionarily‐conserved SNF 1/ AMPK /Sn RK 1 protein kinase family that contributes to cellular energy homeostasis. Functional as heterotrimers, family members comprise a catalytic α subunit and non‐catalytic β and γ subunits; multiple isoforms of each subunit type exist, giving rise to various isoenzymes. The Arabidopsis thaliana genome contains homologues of each subunit type, and, in addition, two atypical subunits, β 3 and βγ, with unique domain architecture, that are found only amongst plants, suggesting atypical heterotrimers. The At Sn RK 1 subunit structure was determined using recombinant protein expression and endogenous co‐immunoprecipitation, and six unique isoenzyme combinations were identified. Each heterotrimeric isoenzyme comprises a catalytic α subunit together with the unique βγ subunit and one of three non‐catalytic β subunits: β 1 , β 2 or the plant‐specific β 3 isoform. Thus, the At Sn RK 1 heterotrimers contain the atypical βγ subunit rather than a conventional γ subunit. Mammalian AMPK heterotrimers are phosphorylated on the T–loop ( pT hr175/176) within both catalytic a subunits. However, At Sn RK 1 is insensitive to AMP and ADP , and is resistant to T–loop dephosphorylation by protein phosphatases, a process that inactivates other SNF 1/ AMPK family members. In addition, we show that Sn RK 1 is inhibited by a heat‐labile, >30 kDa, soluble proteinaceous factor that is present in the lysate of young rosette leaves. Finally, none of the three Sn RK 1 carbohydrate‐binding modules, located in the β 1 , β 2 and βγ subunits, associate with various carbohydrates, including starch, the plant analogue of glycogen to which AMPK binds in vitro . These data clearly demonstrate that At Sn RK 1 is an atypical member of the SNF 1/ AMPK /Sn RK 1 family.