Jan Eric B. Chavez
Phosphoinositide 3-Kinase regulates
glycolysis through mobilization of
Aldolase A from the actin cytoskeleton
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Corresponding author: Gerburg M Wulf
1Medicine,
Beth Israel Deaconess Medical Center, Boston, MA, USA
2Medicine,
Weil Cornell Medical College, New York, NY, USA
3Biology,
Boston University, Boston, NY, USA
4University
of California, Davis, CA, USA
Published:
28 May 2014
© 2014 Hu et al; licensee BioMed Central Ltd.
Background
Phosphoinositide 3-Kinase (PI3K) has been shown to modulate multiple steps in glucose uptake
and metabolism through activation of the protein kinase, AKT. In order to dissect the
contributions of PI3K-pathway components, we examined the effects of specific enzyme
inhibitors on the regulation of glycolysis
.
PIK-93 inhibitor (yellow) bound to the PI3 Kinase 110 gamma subunit (source:
http://en.wikipedia.org/wiki/Phosphoinositide_3-kinase)
Methods
We measured reduction of NAD to NADH, occurring at the GAPDH step, as a read-out for
glycolysis in living cells; mass spectroscopy to determine the relative abundance of glycolytic
metabolites in breast cell cultures and in a mouse model of breast cancer; immunoblotting and
confocal live cell microscopy to delineate the intracellular signaling cascade downstream from
PI3K and a spectrophotometric assay to determine Aldolase activity.
Results
In breast epithelial cells PI3K-, but not AKT-, SGK- or mTOR-inhibitors cause a significant
decrease in glycolysis at the step catalyzed by Aldolase A. We show that growth factors
stimulate Aldolase A release from the actin cytoskeleton and an increase in cellular Aldolase
activity in a PI3K dependent manner. The mobilization and activation of Aldolase is dependent
on Rac1-catalyzed phosphorylation of p-21 activated kinase (PAK) and subsequent mobilization
of the actin cytoskeleton.
Conclusions
This newly identified AKT- and mTOR-independent role of PI3K in controlling glucose
metabolism has important implications in regard to utilization of PI3K pathway inhibitors for
treatment of epithelial cancers.
I.
1.
Chemical reactions:
The Phosphatase and Tensin homolog deleted from chromosome ten
(PTEN)/phosphatidylinositol 3 kinase (PI3K) network regulates many facets of cancer
biology. Pictured is a simplistic schematic representation of the PTEN/PI3K pathway in
cancer. Lines represent direct or indirect activation (arrow head) or inactivation (blunt
end) by various signaling molecules. In essence, certain growth factor receptor tyrosine
kinases and Ras activate PI3K, leading to an increase in the cellular levels of
phosphatidylinositol 3,4,5 tri-phosphate (PIP3). PIP3 binds to and activates a subset of
pleckstrin homology domain-containing proteins including the protein kinases PDK1 and
AKT. These kinases in turn regulate many critical processes involved in cancer such as
cell cycle progression, apoptosis and cellular growth/ translation. PTEN acts as a critical
negative regulator of PI3K signaling by removing the D3 phosphate from PIP3 to
produce phosphatidylinositol 4,5 bi-phosphate (PIP2). For simplicity, this figure
predominantly pictures the membrane/cytoplasmic localization of certain PTEN/PI3K
pathway components, even though many of these molecules are also known to reside
and function in the nucleus.
Source: http://www.nature.com/onc/journal/v27/n41/fig_tab/onc2008248f1.html
2.
A model of the function of PI3K signaling in invadopodia formation and cell
invasion. p110α that is activated downstream of growth factor receptors produces the
signaling lipid PI(3,4,5)P3 to regulate invadopodia formation and cancer cell invasion.
PI(3,4)P2 that is generated via dephosphorylation of PI(3,4,5)P3 by synaptojanin-2 (SJ2)
may regulate invadopodia formation through the Tks5/N-WASP axis in parallel with
PI(3,4,5)P3. PDK1 and Akt are activated by both PI(3,4,5)P3 and PI(3,4)P2 and act as
mediators of the PI3K signaling pathway for invadopodia formation.
Source: http://jcb.rupress.org/content/193/7/1275.figures-only
3. Following growth factor stimulation and subsequent activation of receptor tyrosine
kinases (RTKs), class IA phosphoinositide 3-kinases (PI3Ks), consisting of p110 –p85,
p110 –p85 and p110 –p85, are recruited to the membrane by direct interaction of the
p85 subunit with the activated receptors (for example, platelet-derived growth factor
receptor) or by interaction with adaptor proteins associated with the receptors (for
example, insulin receptor substrate 1). The activated p110 catalytic subunit converts
phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P2) to phosphatidylinositol-3,4,5trisphosphate (PtdIns(3,4,5)P3) at the membrane, providing docking sites for signalling
proteins that have pleckstrin homology domains, including putative 3-phosphoinositidedependent kinase 1 (PDPK1) and serine–threonine protein kinase AKT (also known as
protein kinase B). PDPK1 phosphorylates and activates AKT, which elicits a broad range
of downstream signalling events. The class IB PI3K (p110 –p101) can be activated
directly by G protein-coupled receptors (GPCRs) through interaction with the G
subunit of trimeric G proteins. The p110 and p110 subunits can also be activated by
GPCRs. PTEN (phosphatase and tensin homologue) antagonizes the PI3K action by
dephosphorylating PtdIns(3,4,5)P3. BAD, BCL2-associated agonist of cell death;
FOXO1, forkhead box O1 (also known as FKHR); GSK3 , glycogen synthase kinase 3
; mTOR, mammalian target of rapamycin; NF- B, nuclear factor- B; PKC, protein kinase
C; RAC1, RAS-related C3 botulinum toxin substrate 1; SGK, serum and glucocorticoidregulated kinase; S6K, ribosomal protein S6 kinase; LPA, lysophosphatidic acid.
Source: http://www.nature.com/nrd/journal/v8/n8/fig_tab/nrd2926_F1.html
II.
Plausible research (A) and adaptation of the organism concerned (B)
How can the Phosphoinositide 3-Kinase
A. How can the PI3K can be used to treat cancer?
B. -C. PI3K plays a major part in the resistance of tumor cells to conventional cytotoxic
and targeted anticancer therapies. It also play central role in regulation of cell
cycle, apoptosis, DNA repair, senescence, angiogenesis, cellular metabolism,
and motility. They act as intermediate signaling molecules and are most well
known for their roles in the PI3K/AKT/mTOR signaling pathway. PI3Ks transmit
signals from the cell surface to the cytoplasm by generating second messengers
– phosphorylated phosphatidylinositols – which in turn activate multiple effector
kinase pathways, including BTK, AKT, PKC, NF-kappa-B, and JNK/SAPK
pathways, and ultimately result in survival and growth of normal cells. (Source:
http://www.jhoonline.org/content/6/1/88)