Dataset Information

Mechanics of EGF receptor/ErbB2 kinase activation revealed by luciferase fragment complementation imaging.

ABSTRACT: Binding of EGF to its receptor induces dimerization of the normally monomeric receptor. Activation of its intracellular tyrosine kinase then occurs through the formation of an asymmetric kinase dimer in which one subunit, termed the "receiver" kinase, is activated by interaction with the other subunit, termed the "activator" kinase [Zhang, et al. (2006) Cell 125: 1137-1149]. Although there is significant experimental support for this model, the relationship between ligand binding and the mechanics of kinase activation are not known. Here we use luciferase fragment complementation in EGF receptor (EGFR)/ErbB2 heterodimers to probe the mechanics of ErbB kinase activation. Our data support a model in which ligand binding causes the cis-kinase (the EGFR) to adopt the receiver position in the asymmetric dimer and to be activated first. If the EGF receptor is kinase active, this results in the phosphorylation of the trans-kinase (ErbB2). However, if the EGF receptor kinase is kinase dead, the ErbB2 kinase is never activated. Thus, activation of the kinases in the EGFR/ErbB2 asymmetric dimer occurs in a specific sequence and depends on the kinase activity of the EGF receptor.

SUBMITTER: Macdonald-Obermann JL

PROVIDER: S-EPMC3252912 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Mechanics of EGF receptor/ErbB2 kinase activation revealed by luciferase fragment complementation imaging.

Macdonald-Obermann Jennifer L JL Piwnica-Worms David D Pike Linda J LJ

Proceedings of the National Academy of Sciences of the United States of America 20111221 1

Binding of EGF to its receptor induces dimerization of the normally monomeric receptor. Activation of its intracellular tyrosine kinase then occurs through the formation of an asymmetric kinase dimer in which one subunit, termed the "receiver" kinase, is activated by interaction with the other subunit, termed the "activator" kinase [Zhang, et al. (2006) Cell 125: 1137-1149]. Although there is significant experimental support for this model, the relationship between ligand binding and the mechani ...[more]

PMID: 22190492

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Project description:A critical challenge for all organisms is to carefully control the amount of lipids they store. An important node for this regulation is the protein coat present at the surface of lipid droplets (LDs), the intracellular organelles dedicated to lipid storage. Only limited aspects of this regulation are understood so far. For the probably best characterized case, the regulation of lipolysis in mammals, some of the major protein players have been identified, and it has been established that this process crucially depends on an orchestrated set of protein-protein interactions. Proteomic analysis has revealed that LDs are associated with dozens, if not hundreds, of different proteins, most of them poorly characterized, with even fewer data regarding which of them might physically interact. To comprehensively understand the mechanism of lipid storage regulation, it will likely be essential to define the interactome of LD-associated proteins.Previous studies of such interactions were hampered by technical limitations. Therefore, we have developed a split-luciferase based protein-protein interaction assay and test for interactions among 47 proteins from Drosophila and from mouse. We confirmed previously described interactions and identified many new ones. In 1561 complementation tests, we assayed for interactions among 487 protein pairs of which 92 (19%) resulted in a successful luciferase complementation. These results suggest that a prominent fraction of the LD-associated proteome participates in protein-protein interactions.In targeted experiments, we analyzed the two proteins Jabba and CG9186 in greater detail. Jabba mediates the sequestration of histones to LDs. We successfully applied our split luciferase complementation assay to learn more about this function as we were e.g. able to map the interaction between Jabba and histones. For CG9186, expression levels affect the positioning of LDs. Here, we reveal the ubiquitination of CG9186, and link this posttranslational modification to LD cluster induction.

Project description:The regulation of organismic lipid storage amounts is a central goal of all organisms. Proteins associated with the dedicated lipid storage organelles, the so-called lipid droplets (LDs), are instrumental to this regulation. LD proteomes of diverse organisms have been characterized by mass spectrometry. Yet, the functional characterization of most of these proteins is still lagging behind. Moreover, knowledge of interactions among LD-associated proteins is sparse and mostly limited to proteins involved in mammalian lipolysis regulation. This process crucially depends on an orchestrated set of protein-protein interactions which limit the accessibility, and thus remobilization, of the lipid stores. Thus, a better knowledge of the LD-associated protein interactome likely reveals entry points to deeper understand lipid storage regulation on a mechanistic level. Here, we utilize a split-luciferase based protein-protein interaction assay to identify interactions among 46 LD-associated proteins and protein variants of which 40 are Drosophila and 6 mouse proteins. In 1531 complementation tests, we assayed for interactions among 487 luciferase fragment fusion protein pairs (covered by 830 different construct combinations) of which 85 (17.45 %) resulted in a significant luciferase complementation. These results suggest, that a prominent fraction of the LD-associated proteome participates in protein-protein interactions, and provide a basis for further functional studies. Besides confirming previously described interactions, we identified several new protein interaction pairs. Of these, we characterize the following three in greater detail: (i) Jabba and CG9186, (ii) Jabba and Histones and (iii) Ubiquitin and CG9186. The interaction among Jabba and Histones is of physiological significance and we provide data suggesting that Jabba alone is sufficient to recruit Histones to LDs. Further, we identified a positively charged amino acid stretch of 16 amino acids within the Jabba protein which is necessary for the Jabba-Histone interaction. CG9186 is an annotated esterase which is involved in lipid storage amount regulation and positioning of LDs. We present data supporting the ubiquitination of at least two lysine residues of CG9186 and demonstrate a role of CG9186 ubiquitination in the induction of LD clusters linked to the overexpression of CG9186.

Dataset Information

Mechanics of EGF receptor/ErbB2 kinase activation revealed by luciferase fragment complementation imaging.

Publications

Mechanics of EGF receptor/ErbB2 kinase activation revealed by luciferase fragment complementation imaging.

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