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The sheer amplitude of biological actions of insulin-like growth factor I (IGF-1) affecting all types of cells in all tissues suggests a vast signaling landscape for this ubiquitous humoral signal. While the canonical signaling pathways primarily involve the Ras/MAPK and PI3K/AKT cascades, the evolutionary conservation of insulin-like peptides (ILPs) and their pathways hints at the potential for novel functions to emerge over time. Indeed, the evolutionary trajectory of ILPs opens the possibility of either novel functions for these two pathways, novel downstream routes, or both. Evidence supporting this notion includes observations of neofunctionalization in bony fishes or crustaceans, and the involvement of ILPs pathways in invertebrate eusociality or in vertebrate bone physiology, respectively. Such evolutionary processes likely contribute to the rich diversity of ILPs signaling observed today. Moreover, the interplay between conserved signaling pathways, such as those implicated in aging (predominantly involving the PI3K-AKT route), and lesser known pathways, such as those mediated by biased G-protein coupled receptors and others even less known, may underpin the context-dependent actions characteristic of ILPs signaling. While canonical IGF-1 signaling is often assumed to account for the intracellular pathways utilized by this growth factor, a comprehensive analysis of all the pathways mediated by the IGF-1 receptor (IGF-1R) remains lacking. This review aims to explore both canonical and non-canonical routes of IGF-1R action across various cell types, offering a detailed examination of the mechanisms underlying IGF-1 signaling and highlighting the significant gaps in our current understanding.
Keywords
insulin-like growth factor
signaling
insulin receptor substrate 1 (IRS-1)
phosphatidylinositide-3 kinase (PI3K)
AKT (PKB)
Ras protein
Abbreviations
CREB
cAMP response element-binding protein
eNOS
Endothelial nitric oxide synthase
Elk
Ets-like Kinase
FSH
Follicle stimulating hormone
GluT
Glucose transporter
GSK3
Glycogen synthase kinase 3
IGF-1
Insulin-like growth factor 1
IRS
Insulin receptor substrate
LRP
Low-density lipoprotein receptor-related protein
LH
Luteinizing hormone
LPA
Lysophosphatidic acid
mTOR
Mammalian target of rapamycin
MAPK
Mitogen activated protein kinase
MCT
Monocarboxylate transporter
NFκB
Nuclear factor kappa-light-chain-enhancer of activated B cells
NFAT
Nuclear factor of activated T-cells
PTEN
Phosphatase and tensin homolog
PI3K
Phosphatidylinositide-3 kinase
PKC
Protein kinase C
RACK
Receptor for activated C kinase
STAT
Signal transducer and activator of transcription
Shc
Src homolog and collagen domain protein
TSH
Thyroid stimulating hormone
TRPV4
Transient receptor potential vanilloid 4
Wnt
Wingless-Int
© 2024 The Authors. Published by Elsevier Inc on behalf of American Society for Biochemistry and Molecular Biology.