IGF-1 receptor activity in the Golgi of migratory cancer cells depends on adhesion-dependent phosphorylation of Tyr ¹²⁵⁰ and Tyr ¹²⁵¹

Abstract

Although insulin-like growth factor 1 (IGF-1) signaling promotes tumor growth and cancer progression, therapies that target the IGF-1 receptor (IGF-1R) have shown poor clinical efficacy. To address IGF-1R activity in cancer cells and how it differs from that of the closely related insulin receptor (IR), we focused on two tyrosines in the IGF-1R C-terminal tail that are not present in the IR and are essential for IGF-1–mediated cancer cell survival, migration, and tumorigenic growth. We found that Tyr1250 and Tyr1251 (Tyr1250/1251) were autophosphorylated in a cell adhesion–dependent manner. To investigate the consequences of this phosphorylation, we generated phosphomimetic Y1250E/Y1251E (EE) and nonphosphorylatable Y1250F/Y1251F (FF) mutant forms of IGF-1R. Although fully competent in kinase activity and signaling, the EE mutant was more rapidly internalized and degraded than either the wild-type or FF receptor. IGF-1 promoted the accumulation of wild-type and EE IGF-1R within the Golgi apparatus, whereas the FF mutant remained at the plasma membrane. Golgi-associated IGF-1R signaling was a feature of migratory cancer cells, and Golgi disruption impaired IGF-1–induced signaling and cell migration. Upon the formation of new cell adhesions, IGF-1R transiently relocalized to the plasma membrane from the Golgi. Thus, phosphorylation at Tyr1250/1251 promoted IGF-1R translocation to and signaling from the Golgi to support an aggressive cancer phenotype. This process distinguishes IGF-1R from IR signaling and could contribute to the poor clinical efficacy of antibodies that target IGF-1R on the cell surface.

Controlled Signaling—Insulin-Like Growth Factor Receptor Endocytosis and Presence at Intracellular Compartments

“…Although IGF-1R kinase activity is clearly essential for recruiting the proteins that facilitate receptor internalization and ubiquitination, it is not understood how the C-terminal tail contributes to ubiquitin-mediated IGF-1R trafficking and degradation. Our recent study showed that IGF-1promoted phosphorylation of the Tyr 1250/1251 site in the IGF-1R C-terminal results in enhanced IGF-1R internalization and proteosomal degradation (22). However, whether the Tyr 1250/1251 phospho-site is involved in or modulates IGF-1R ubiquitination is still unknown.…”

“…CCP/caveolin-vesicles that contain internalized IGF-1R become fused with early endosomes (27,40,44,52). Here the IGF-1R proteins are sorted, either targeted for degradation (24,35), transported toward the Golgi network (22), transported to the nucleus (20,(53)(54)(55)(56), or recycled back to the plasma membrane (57) (Figure 1B). Internalized ubiquitinated proteins can be detected by distinct multiprotein complexes that comprise the endosomal sorting complex required for transport (ESCRT) (58-61) and serve as signal for cargo sorting (58).…”

“…Although once thought that when cell surface RTKs are internalized, their signal transduction is terminated, it is now generally accepted that internalized receptors, including the IGF-1R may signal from endosomal and intracellular membrane compartments, or may also regulate gene transcription by translocating to the nucleus (16)(17)(18)(19)(20)(21)(22). However, the mechanisms of intracellular trafficking and which signals determine the subcellular localization of the IGF-1R or its compartmentalization with other signaling proteins are not known.…”

“…However, the mechanisms of intracellular trafficking and which signals determine the subcellular localization of the IGF-1R or its compartmentalization with other signaling proteins are not known. Recent studies suggest that these events are regulated in a cell type-specific way and that cell-specific signals may influence the recruitment and activation of effector proteins (20,22). Therefore, the cell-specific IGF-1R trafficking, compartmentalization and its subcellular location may define how cells respond to different extracellular stimuli.…”

Thiophosphopeptides Instantly Targeting Golgi Apparatus and Selectively Killing Cancer Cells

“…[1][2] Increasing numbers of studies have revealed that Golgi is a hub for different signaling pathways that drive the survival and migration of cancer cells. [3][4][5] Although Golgi is emerging as an important target for cancer therapy, there are, however, few approaches for targeting Golgi. [6][7] While Golgi mannosidase II inhibitors are able to inhibit cancer cells, the selectivity 8 or efficacy 6 of the inhibitors remains to be improved.…”