SUMO‐modified insulin‐like growth factor 1 receptor (IGF‐1R) increases cell cycle progression and cell proliferation

Abstract

Increasing number of studies have shown nuclear localization of the insulin‐like growth factor 1 receptor (nIGF‐1R) in tumor cells and its links to adverse clinical outcome in various cancers. Any obvious cell physiological roles of nIGF‐1R have, however, still not been disclosed. Previously, we reported that IGF‐1R translocates to cell nucleus and modulates gene expression by binding to enhancers, provided that the receptor is SUMOylated. In this study, we constructed stable transfectants of wild type IGF1R (WT) and triple‐SUMO‐site‐mutated IGF1R (TSM) using igf1r knockout mouse fibroblasts (R‐). Cell clones (R‐WT and R‐TSM) expressing equal amounts of IGF‐1R were selected for experiments. Phosphorylation of IGF‐1R, Akt, and Erk upon IGF‐1 stimulation was equal in R‐WT and R‐TSM. WT was confirmed to enter nuclei. TSM did also undergo nuclear translocation, although to a lesser extent. This may be explained by that TSM heterodimerizes with insulin receptor, which is known to translocate to cell nuclei. R‐WT proliferated substantially faster than R‐TSM, which did not differ significantly from the empty vector control. Upon IGF‐1 stimulation G1‐S‐phase progression of R‐WT increased from 12 to 38%, compared to 13 to 20% of R‐TSM. The G1‐S progression of R‐WT correlated with increased expression of cyclin D1, A, and CDK2, as well as downregulation of p27. This suggests that SUMO‐IGF‐1R affects upstream mechanisms that control and coordinate expression of cell cycle regulators. Further studies to identify such SUMO‐IGF‐1R dependent mechanisms seem important.

Melatonin disturbs SUMOylation‐mediated crosstalk between c‐Myc and nestin via MT1 activation and promotes the sensitivity of paclitaxel in brain cancer stem cells

“…Melatonin reduced the expression of SUMO‐1 more than SUMO‐2 and SUMO‐3 in X02 cells by qRT‐PCR (Figure A). As it was well‐known that many proteins including p53, c‐Myc, and others can be sumoylated, SUMOylation of nestin was investigated in X02 cells. Interestingly, SUMO‐1 overexpression upregulated the expression of nestin, without affecting c‐Myc, and also reduced the inhibitory effect of melatonin on nestin and c‐Myc in X02 cells transfected with HA‐SUMO‐1 plasmid (Figure B).…”

Nuclear insulin-like growth factor 1 receptor phosphorylates proliferating cell nuclear antigen and rescues stalled replication forks after DNA damage

“…Further confirmation was achieved by using R-TSM cells (RϪ transfected with triple SUMO-site-mutated IGF-1R cell line). Just recently we showed that R-TSM cells exhibited diminished nuclear gene regulatory effects of IGF-1R while retaining IGF-1R kinase-dependent signaling (2,24).…”

“…MEF igf1r Ϫ/Ϫ (RϪ-) and RϪ cells overexpressing IGF-1R (Rϩ) were from Dr. R. Baserga (Thomas Jefferson University, PA). The R-WT (RϪ with newly transfected WT IGF-1R), R-TSM (RϪ transfected with SUMOmutated IGF-1R), and RϪPuro (empty vector control) were obtained as described elsewhere (24). All cell lines were cultured in DMEM with 10% FBS, with the exception of Gm02808 being cultured in DMEM/F-12 with 20% FBS.…”

New Insights from IGF-IR Stimulating Activity Analyses: Pathological Considerations

“…It has been reported that nuclear IGF-IR is a feature of pre-invasive lesions and invasive cancers including prostate, renal and breast cancers, and an association between nuclear IGF-IR and adverse prognosis was identified in renal cancer [79]. Subsequent data did associate nuclear IGF-IR with proliferation, tumorigenicity, resistance to EGFR inhibition and clinical response to therapeutic anti-IGF-IR antibodies, which suggests that IGF-IR nuclear import has biological significance and may contribute directly to IGF-IR function [79,[85][86][87][88][89][90].…”