title: Essential roles of PI(3)K-p110beta in cell growth, metabolism and tumorigenesis.
abstract: On activation by receptors, the ubiquitously expressed class IA isoforms (p110alpha and p110beta) of phosphatidylinositol-3-OH kinase (PI(3)K) generate lipid second messengers, which initiate multiple signal transduction cascades. Recent studies have demonstrated specific functions for p110alpha in growth factor and insulin signalling. To probe for distinct functions of p110beta, we constructed conditional knockout mice. Here we show that ablation of p110beta in the livers of the resulting mice leads to impaired insulin sensitivity and glucose homeostasis, while having little effect on phosphorylation of Akt, suggesting the involvement of a kinase-independent role of p110beta in insulin metabolic action. Using established mouse embryonic fibroblasts, we found that removal of p110beta also had little effect on Akt phosphorylation in response to stimulation by insulin and epidermal growth factor, but resulted in retarded cell proliferation. Reconstitution of p110beta-null cells with a wild-type or kinase-dead allele of p110beta demonstrated that p110beta possesses kinase-independent functions in regulating cell proliferation and trafficking. However, the kinase activity of p110beta was required for G-protein-coupled receptor signalling triggered by lysophosphatidic acid and had a function in oncogenic transformation. Most strikingly, in an animal model of prostate tumour formation induced by Pten loss, ablation of p110beta (also known as Pik3cb), but not that of p110alpha (also known as Pik3ca), impeded tumorigenesis with a concomitant diminution of Akt phosphorylation. Taken together, our findings demonstrate both kinase-dependent and kinase-independent functions for p110beta, and strongly indicate the kinase-dependent functions of p110beta as a promising target in cancer therapy.
authors.affiliation: Department of Cancer Biology, Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA.
authors.forename: Shidong
authors.initials: S
authors.lastname: Jia
authors.forename: Zhenning
authors.initials: Z
authors.lastname: Liu
authors.forename: Sen
authors.initials: S
authors.lastname: Zhang
authors.forename: Pixu
authors.initials: P
authors.lastname: Liu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Sang Hyun
authors.initials: SH
authors.lastname: Lee
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Sabina
authors.initials: S
authors.lastname: Signoretti
authors.forename: Massimo
authors.initials: M
authors.lastname: Loda
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Roberts
authors.forename: Jean J
authors.initials: JJ
authors.lastname: Zhao
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002471:Cell Transformation, Neoplastic; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology; D005947:Glucose / Q000378:metabolism*; D018149:Glucose Intolerance / Q000201:enzymology / Q000235:genetics; D006706:Homeostasis; D006801:Humans; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007333:Insulin Resistance / Q000235:genetics; D008099:Liver / Q000201:enzymology / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D051059:PTEN Phosphohydrolase / Q000172:deficiency / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011471:Prostatic Neoplasms / Q000201:enzymology / Q000235:genetics / Q000473:pathology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D007328:Insulin; D004815:Epidermal Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase; C487757:Pten protein, mouse; D005947:Glucose