Insulin and Insulin-like Growth Factor II Differentially Regulate Endocytic Sorting and Stability of Insulin Receptor Isoform A
Brzozowski, Andrzej M.
Iozzo, Renato V.
Insulin-like growth factor (IGF)
Insulin receptor isoform A
Permanent link to this recordhttp://hdl.handle.net/20.500.12613/7096
MetadataShow full item record
AbstractThe insulin receptor isoform A (IR-A) binds both insulin and insulin-like growth factor (IGF)-II, although the affinity for IGF-II is 3–10-fold lower than insulin depending on a cell and tissue context. Notably, in mouse embryonic fibroblasts lacking the IGF-IR and expressing solely the IR-A (R−/IR-A), IGF-II is a more potent mitogen than insulin. As receptor endocytosis and degradation provide spatial and temporal regulation of signaling events, we hypothesized that insulin and IGF-II could affect IR-A biological responses by differentially regulating IR-A trafficking. Using R−/IR-A cells, we discovered that insulin evoked significant IR-A internalization, a process modestly affected by IGF-II. However, the differential internalization was not due to IR-A ubiquitination. Notably, prolonged stimulation of R−/IR-A cells with insulin, but not with IGF-II, targeted the receptor to a degradative pathway. Similarly, the docking protein insulin receptor substrate 1 (IRS-1) was down-regulated after prolonged insulin but not IGF-II exposure. Similar results were also obtained in experiments using [NMeTyrB26]-insulin, an insulin analog with IR-A binding affinity similar to IGF-II. Finally, we discovered that IR-A was internalized through clathrin-dependent and -independent pathways, which differentially regulated the activation of downstream effectors. Collectively, our results suggest that a lower affinity of IGF-II for the IR-A promotes lower IR-A phosphorylation and activation of early downstream effectors vis à vis insulin but may protect IR-A and IRS-1 from down-regulation thereby evoking sustained and robust mitogenic stimuli.
CitationAlaide Morcavallo, Marco Genua, Angela Palummo, Emilia Kletvikova, Jiri Jiracek, Andrzej M. Brzozowski, Renato V. Iozzo, Antonino Belfiore, Andrea Morrione. Insulin and Insulin-like Growth Factor II Differentially Regulate Endocytic Sorting and Stability of Insulin Receptor Isoform A*, Journal of Biological Chemistry, 287,(14), 2012, 11422-11436, ISSN 0021-9258, https://doi.org/10.1074/jbc.M111.252478.
Citation to related workElsevier
Has partJournal of Biological Chemistry, Vol. 287, No. 14
ADA complianceFor Americans with Disabilities Act (ADA) accommodation, including help with reading this content, please contact email@example.com
Showing items related by title, author, creator and subject.
Ligand-mediated endocytosis and trafficking of the insulin-like growth factor receptor I and insulin receptor modulate receptor functionMorcavallo, Alaide; Stefanello, Manuela; Iozzo, Renato V.; Belfiore, Antonino; Morrione, Andrea; Morrione|0000-0002-2319-7884 (2014-12-17)The insulin-like growth factor system and its two major receptors, the IGF receptor I (IGF-IR) and IR, plays a central role in a variety of physiological cellular processes including growth, differentiation, motility, and glucose homeostasis. The IGF-IR is also essential for tumorigenesis through its capacity to protect cancer cells from apoptosis. The IR is expressed in two isoforms: the IR isoform A (IR-A) and isoform B (IR-B). While the role of the IR-B in the regulation of metabolic effects has been known for several years, more recent evidence suggests that the IR, and in particular the IR-A, may be involved in the pathogenesis of cancer. Ligand-mediated endocytosis of tyrosine-kinases receptors plays a critical role in modulating the duration and intensity of receptors action but while the signaling pathways induced by the IGF-IR and IR are quite characterized, very little is still known about the mechanisms and proteins that regulate ligand-induced IGF-IR and IR endocytosis and trafficking. In addition, how these processes affect receptor downstream signaling has not been fully characterized. Here, we discuss the current understanding of the mechanisms and proteins regulating IGF-IR and IR endocytosis and sorting and their implications in modulating ligand-induced biological responses.
Insulin Receptor Isoform A Modulates Metabolic Reprogramming of Breast Cancer Cells in Response to IGF2 and Insulin StimulationVella, Veronica; Nicolosi, Maria Luisa; Giuliano, Marika; Morrione, Andrea; Malaguarnera, Roberta; Belfiore, Antonino; Morrione|0000-0002-2319-7884 (2019-09-01)Previously published work has demonstrated that overexpression of the insulin receptor isoform A (IR-A) might play a role in cancer progression and metastasis. The IR has a predominant metabolic role in physiology, but the potential role of IR-A in cancer metabolic reprogramming is unknown. We aimed to characterize the metabolic impact of IR-A and its ligand insulin like growth factor 2 (IGF2) in human breast cancer (BC) cells. To establish autocrine IGF2 action, we generated human BC cells MCF7 overexpressing the human IGF2, while we focused on the metabolic effect of IR-A by stably infecting IGF1R-ablated MCF7 (MCF7IGF1R-ve) cells with a human IR-A cDNA. We then evaluated the expression of key metabolism related molecules and measured real-time extracellular acidification rates and oxygen consumption rates using the Seahorse technology. MCF7/IGF2 cells showed increased proliferation and invasion associated with aerobic glycolysis and mitochondrial biogenesis and activity. In MCF7IGF1R-ve/IR-A cells insulin and IGF2 stimulated similar metabolic changes and were equipotent in eliciting proliferative responses, while IGF2 more potently induced invasion. The combined treatment with the glycolysis inhibitor 2-deoxyglucose (2DG) and the mitochondrial inhibitor metformin blocked cell invasion and colony formation with additive effects. Overall, these results indicate that IGF2 and IR-A overexpression may contribute to BC metabolic reprogramming.
Deletion of LDLRAP1 Induces Atherosclerotic Plaque Formation, Insulin Resistance, and Dysregulated Insulin Response in Adipose TissueAutieri, Michael V.; Scalia, Rosario; Yu, Jun; Rizzo, Victor; Kilpatrick, Laurie; Bellas, Evangelia (Temple University. Libraries, 2022)Atherosclerosis and symptoms of metabolic syndrome such as obesity, high cholesterol, and insulin resistance often coincide and exacerbate one another, but the cellular and molecular events in common with these conditions have not yet been fully elucidated. Low density lipoprotein receptor adaptor protein 1 (LDLRAP1) is an adaptor protein which interacts with the cytoplasmic tail of the LDL receptor, internalizing the receptor when it engages with LDL. Mutations in this gene lead to LDLR malfunction and cause Autosomal Recessive Hypercholesterolemia (ARH) in humans; however, direct causality on atherogenesis or metabolism in a defined pre-clinical model has not been reported. The aim of this study was to test the hypothesis that deletion of LDLRAP1 would lead to hypercholesterolemia and atherosclerosis. LDLRAP1-/- mice fed a high fat, western diet (HFD) for 16 weeks had significantly increased plasma cholesterol and triglyceride concentrations, accompanied with significantly increased plaque burden compared with wild-type controls. Unexpectedly, LDLRAP1-/- mice gained significantly more weight compared to the wild-type, LDLRAP1-/- mice were insulin resistant, and calorimetric studies suggested an altered metabolic profile. We determined that LDLRAP1 is highly expressed in white adipose tissue (WAT), and LDLRAP1-/- adipocytes are significantly larger and have reduced glucose uptake and AKT phosphorylation, but increased CD36 expression. WAT from LDLRAP1-/- mice is hypoxic, and has gene expression signatures of dysregulated lipid storage and energy homeostasis. These data indicate that lack of LDLRAP1 directly leads to atherosclerosis in mice, and also are the first to suggest that LDLRAP1 plays an unanticipated metabolic regulatory role in adipose tissue. LDLRAP1 deletion leads to systemic effects, and may act as a molecular link which regulates dyslipidemia, atherosclerosis, insulin resistance, and obesity.