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Molecular mechanism of activation of class IA phosphoinositide 3-kinases (PI3Ks)
by membrane-localized HRas
#MMPMID28515318
Siempelkamp BD
; Rathinaswamy MK
; Jenkins ML
; Burke JE
J Biol Chem
2017[Jul]; 292
(29
): 12256-12266
PMID28515318
show ga
Class IA PI3Ks are involved in the generation of the key lipid signaling molecule
phosphatidylinositol 3,4,5-trisphosphate (PIP(3)), and inappropriate activation
of this pathway is implicated in a multitude of human diseases, including cancer,
inflammation, and primary immunodeficiencies. Class IA PI3Ks are activated
downstream of the Ras superfamily of GTPases, and Ras-PI3K interaction plays a
key role in promoting tumor formation and maintenance in Ras-driven tumors.
Investigating the detailed molecular events in the Ras-PI3K interaction has been
challenging because it occurs on a membrane surface. Here, using
maleimide-functionalized lipid vesicles, we successfully generated
membrane-resident HRas and evaluated its effect on PI3K signaling in lipid kinase
assays and through analysis with hydrogen-deuterium exchange MS. We screened all
class IA PI3K isoforms and found that HRas activates both p110? and p110?
isoforms but does not activate p110?. The p110? and p110? activation by Ras was
synergistic with activation by a soluble phosphopeptide derived from receptor
tyrosine kinases. Hydrogen-deuterium exchange MS revealed that membrane-resident
HRas, but not soluble HRas, enhances conformational changes associated with
membrane binding by increasing membrane recruitment of both p110? and p110?.
Together, these results afford detailed molecular insight into the Ras-PI3K
signaling complex, provide a framework for screening Ras inhibitors, and shed
light on the isoform specificity of Ras-PI3K interactions in a native membrane
context.
|*Models, Molecular
[MESH]
|*Second Messenger Systems
[MESH]
|Amino Acid Substitution
[MESH]
|Animals
[MESH]
|Class I Phosphatidylinositol 3-Kinases/chemistry/genetics/*metabolism
[MESH]
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