The IQGAP scaffolds: Critical nodes bridging receptor activation to cellular signaling

The scaffold protein IQGAP1 assembles multiprotein signaling complexes to influence biological functions. Cell surface receptors, particularly receptor tyrosine kinases and G-protein coupled receptors, are common IQGAP1 binding partners. Interactions with IQGAP1 modulate receptor expression, activation, and/or trafficking. Moreover, IQGAP1 couples extracellular stimuli to intracellular outcomes via scaffolding of signaling proteins downstream of activated receptors, including mitogen-activated protein kinases, constituents of the phosphatidylinositol 3-kinase pathway, small GTPases, and beta-arrestins. Reciprocally, some receptors influence IQGAP1 expression, subcellular localization, binding properties, and post-translational modifications. Importantly, the receptor:IQGAP1 crosstalk has pathological implications ranging from diabetes and macular degeneration to carcinogenesis. Here, we describe the interactions of IQGAP1 with receptors, summarize how they modulate signaling, and discuss their contribution to pathology. We also address the emerging functions in receptor signaling of IQGAP2 and IQGAP3, the other human IQGAP proteins. Overall, this review emphasizes the fundamental roles of IQGAPs in coupling activated receptors to cellular homeostasis.

Automated summary

The scaffold protein IQGAP1 assembles complexes with multiple signaling proteins to influence biological functions. It interacts with cell surface receptors, modulating their expression, activation, and trafficking. IQGAP1 also links extracellular stimuli to intracellular outcomes by scaffolding signaling proteins downstream of activated receptors. This receptor:IQGAP1 crosstalk has pathological implications and contributes to diseases like diabetes, macular degeneration, and carcinogenesis.