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1.
Proc Natl Acad Sci U S A ; 118(33)2021 08 17.
Artigo em Inglês | MEDLINE | ID: mdl-34385319

RESUMO

The protein kinase Akt is one of the primary effectors of growth factor signaling in the cell. Akt responds specifically to the lipid second messengers phosphatidylinositol-3,4,5-trisphosphate [PI(3,4,5)P3] and phosphatidylinositol-3,4-bisphosphate [PI(3,4)P2] via its PH domain, leading to phosphorylation of its activation loop and the hydrophobic motif of its kinase domain, which are critical for activity. We have now determined the crystal structure of Akt1, revealing an autoinhibitory interface between the PH and kinase domains that is often mutated in cancer and overgrowth disorders. This interface persists even after stoichiometric phosphorylation, thereby restricting maximum Akt activity to PI(3,4,5)P3- or PI(3,4)P2-containing membranes. Our work helps to resolve the roles of lipids and phosphorylation in the activation of Akt and has wide implications for the spatiotemporal control of Akt and potentially lipid-activated kinase signaling in general.

2.
Sci Adv ; 7(35)2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34452907

RESUMO

The class IB phosphoinositide 3-kinase (PI3K), PI3Kγ, is a master regulator of immune cell function and a promising drug target for both cancer and inflammatory diseases. Critical to PI3Kγ function is the association of the p110γ catalytic subunit to either a p101 or p84 regulatory subunit, which mediates activation by G protein-coupled receptors. Here, we report the cryo-electron microscopy structure of a heterodimeric PI3Kγ complex, p110γ-p101. This structure reveals a unique assembly of catalytic and regulatory subunits that is distinct from other class I PI3K complexes. p101 mediates activation through its Gßγ-binding domain, recruiting the heterodimer to the membrane and allowing for engagement of a secondary Gßγ-binding site in p110γ. Mutations at the p110γ-p101 and p110γ-adaptor binding domain interfaces enhanced Gßγ activation. A nanobody that specifically binds to the p101-Gßγ interface blocks activation, providing a novel tool to study and target p110γ-p101-specific signaling events in vivo.

3.
Methods Mol Biol ; 2263: 465-485, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33877613

RESUMO

Cellular membranes are a central hub for initiation and execution of many signaling processes. Integral to these processes being accomplished appropriately is the highly controlled recruitment and assembly of proteins at membrane surfaces. The study of the molecular mechanisms that mediate protein-membrane interactions can be facilitated by utilizing hydrogen-deuterium exchange mass spectrometry (HDX-MS). HDX-MS is a robust analytical technique that allows for the measurement of the exchange rate of backbone amide hydrogens with solvent to make inferences about protein structure and conformation. This chapter discusses the use of HDX-MS as a tool to study the conformational changes that occur within peripheral membrane proteins upon association with membrane. Particular reference will be made to the analysis of the protein kinase Akt and its activation upon binding phosphatidylinositol (3,4,5) tris-phosphate (PIP3)-containing membranes to illustrate specific methodological principles.


Assuntos
Membrana Celular/metabolismo , Proteínas Proto-Oncogênicas c-akt/química , Proteínas Proto-Oncogênicas c-akt/metabolismo , Fenômenos Biofísicos , Membrana Celular/química , Espectrometria de Massa com Troca Hidrogênio-Deutério , Simulação de Dinâmica Molecular , Fosfatos de Fosfatidilinositol/química , Ligação Proteica , Conformação Proteica , Proteômica
4.
Structure ; 28(2): 145-156.e5, 2020 02 04.
Artigo em Inglês | MEDLINE | ID: mdl-31831213

RESUMO

The class I phosphoinositide 3-kinases (PI3Ks) are key signaling enzymes composed of a heterodimer of a p110 catalytic subunit and a p85 regulatory subunit, with PI3K mutations being causative of multiple human diseases including cancer, primary immunodeficiencies, and developmental disorders. Mutations in the p85α regulatory subunit encoded by PIK3R1 can both activate PI3K through oncogenic truncations in the iSH2 domain, or inhibit PI3K through developmental disorder mutations in the cSH2 domain. Using a combined biochemical and hydrogen deuterium exchange mass spectrometry approach we have defined the molecular basis for how these mutations alter the activity of p110α/p110δ catalytic subunits. We find that the oncogenic Q572∗ truncation of PIK3R1 disrupts all p85-inhibitory inputs, with p110α being hyper-activated compared with p110δ. In addition, we find that the R649W mutation in the cSH2 of PIK3R1 decreases sensitivity to activation by receptor tyrosine kinases. This work reveals unique insight into isoform-specific regulation of p110s by p85α.


Assuntos
Classe I de Fosfatidilinositol 3-Quinases/metabolismo , Classe Ia de Fosfatidilinositol 3-Quinase/genética , Mutação , Domínio Catalítico , Classe I de Fosfatidilinositol 3-Quinases/química , Classe Ia de Fosfatidilinositol 3-Quinase/química , Ativação Enzimática , Humanos , Espectrometria de Massa com Troca Hidrogênio-Deutério , Modelos Moleculares , Conformação Proteica , Domínios Proteicos
5.
EMBO Rep ; 21(2): e48441, 2020 02 05.
Artigo em Inglês | MEDLINE | ID: mdl-31829496

RESUMO

The lipid kinase PI4KB, which generates phosphatidylinositol 4-phosphate (PI4P), is a key enzyme in regulating membrane transport and is also hijacked by multiple picornaviruses to mediate viral replication. PI4KB can interact with multiple protein binding partners, which are differentially manipulated by picornaviruses to facilitate replication. The protein c10orf76 is a PI4KB-associated protein that increases PI4P levels at the Golgi and is essential for the viral replication of specific enteroviruses. We used hydrogen-deuterium exchange mass spectrometry to characterize the c10orf76-PI4KB complex and reveal that binding is mediated by the kinase linker of PI4KB, with formation of the heterodimeric complex modulated by PKA-dependent phosphorylation. Complex-disrupting mutations demonstrate that PI4KB is required for membrane recruitment of c10orf76 to the Golgi, and that an intact c10orf76-PI4KB complex is required for the replication of c10orf76-dependent enteroviruses. Intriguingly, c10orf76 also contributed to proper Arf1 activation at the Golgi, providing a putative mechanism for the c10orf76-dependent increase in PI4P levels at the Golgi.


Assuntos
Enterovirus , Animais , Enterovirus/genética , Enterovirus/metabolismo , Complexo de Golgi/metabolismo , Fosfatos de Fosfatidilinositol , Fosfotransferases (Aceptor do Grupo Álcool)/genética , Fosfotransferases (Aceptor do Grupo Álcool)/metabolismo , Ligação Proteica , Células Sf9 , Replicação Viral
6.
Nat Commun ; 9(1): 3772, 2018 09 14.
Artigo em Inglês | MEDLINE | ID: mdl-30217979

RESUMO

The GTPase Rab11 plays key roles in receptor recycling, oogenesis, autophagosome formation, and ciliogenesis. However, investigating Rab11 regulation has been hindered by limited molecular detail describing activation by cognate guanine nucleotide exchange factors (GEFs). Here, we present the structure of Rab11 bound to the GEF SH3BP5, along with detailed characterization of Rab-GEF specificity. The structure of SH3BP5 shows a coiled-coil architecture that mediates exchange through a unique Rab-GEF interaction. Furthermore, it reveals a rearrangement of the switch I region of Rab11 compared with solved Rab-GEF structures, with a constrained conformation when bound to SH3BP5. Mutation of switch I provides insights into the molecular determinants that allow for Rab11 selectivity over evolutionarily similar Rab GTPases present on Rab11-positive organelles. Moreover, we show that GEF-deficient mutants of SH3BP5 show greatly decreased Rab11 activation in cellular assays of active Rab11. Overall, our results give molecular insight into Rab11 regulation, and how Rab-GEF specificity is achieved.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Fatores de Troca do Nucleotídeo Guanina/ultraestrutura , Proteínas rab de Ligação ao GTP/ultraestrutura , Cristalografia , Escherichia coli , Fatores de Troca do Nucleotídeo Guanina/metabolismo , Humanos , Estrutura Molecular , Mutação , Ligação Proteica , Proteínas rab de Ligação ao GTP/metabolismo
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