The phosphotyrosine interactome of the insulin receptor family and its substrates IRS-1 and IRS-2

Type 2 Diabetes Mellitus Exacerbates Pathological Processes of Parkinson's Disease: Insights from Signaling Pathways Mediated by Insulin Receptors

Parkinson's disease (PD), a chronic and common neurodegenerative disease, is characterized by the progressive loss of dopaminergic neurons in the dense part of the substantia nigra and abnormal aggregation of alpha-synuclein. Type 2 diabetes mellitus (T2DM) is a metabolic disease characterized by chronic insulin resistance and deficiency in insulin secretion. Extensive evidence has confirmed shared pathogenic mechanisms underlying PD and T2DM, such as oxidative stress caused by insulin resistance, mitochondrial dysfunction, inflammation, and disorders of energy metabolism. Conventional drugs for treating T2DM, such as metformin and glucagon-like peptide-1 receptor agonists, affect nerve repair. Even drugs for treating PD, such as levodopa, can affect insulin secretion. This review summarizes the relationship between PD and T2DM and related therapeutic drugs from the perspective of insulin signaling pathways in the brain.

Unraveling the Mystery of Insulin Resistance: From Principle Mechanistic Insights and Consequences to Therapeutic Interventions

Insulin resistance (IR) is a significant factor in the development and progression of metabolic-related diseases like dyslipidemia, T2DM, hypertension, nonalcoholic fatty liver disease, cardiovascular and cerebrovascular disorders, and cancer. The pathogenesis of IR depends on multiple factors, including age, genetic predisposition, obesity, oxidative stress, among others. Abnormalities in the insulin-signaling cascade lead to IR in the host, including insulin receptor abnormalities, internal environment disturbances, and metabolic alterations in the muscle, liver, and cellular organelles. The complex and multifaceted characteristics of insulin signaling and insulin resistance envisage their thorough and comprehensive understanding at the cellular and molecular level. Therapeutic strategies for IR include exercise, dietary interventions, and pharmacotherapy. However, there are still gaps to be addressed, and more precise biomarkers for associated chronic diseases and lifestyle interventions are needed. Understanding these pathways is essential for developing effective treatments for IR, reducing healthcare costs, and improving quality of patient life.

Aerobic exercise attenuates high-fat diet-induced glycometabolism impairments in skeletal muscle of rat: role of EGR-1/PTP1B signaling pathway

OBJECTIVE

Impaired skeletal muscle glycogen synthesis contributes to insulin resistance (IR). Aerobic exercise reported to ameliorate IR by augmenting insulin signaling, however the detailed mechanism behind this improvement remains unclear. This study investigated whether aerobic exercise enhances glycogen anabolism and insulin sensitivity via EGR-1/PTP1B signaling pathway in skeletal muscle of rats.

METHODS

Sprague-Dawley rats fed a high-fat diet (HFD), and performed treadmill exercise training for 6-week. Oral glucose tolerance test was conducted to confirm the IR. Periodic Acid-Schiff (PAS) staining and anthrone colorimetry were used to assess the skeletal muscle glycogen. RT-qPCR, western blot, and immunofluorescence were used to detect the EGR-1/PTP1B pathway and associated signaling molecules.

RESULTS

We found that exercise training significantly decreased blood glucose, insulin, and homeostasis model assessment for IR (HOMA-IR) against HFD-induced elevation. Decreased muscle glycogen content due to HFD was significantly restored after exercise training. Exercise training promoted mRNA expressions of Irs1, Akt, and Glut4, while inhibited Gsk-3β expression against HFD. Next, the decreased IRS1 (phosphorylated/total), AKT (phosphorylated/total), and GLUT4, and increased GSK-3β proteins with HFD were significantly reversed by exercise. Furthermore, HFD-induced overexpression of EGR-1 and PTP1B evidenced by mRNA, protein, and immunofluorescence intensity, were substantially inhibited by exercise, which may contribute to promote insulin sensitivity and glycogen anabolism.

CONCLUSIONS

Aerobic exercise training promotes insulin sensitivity and skeletal muscle glycogen synthesis in HFD-fed rats. The beneficial effects of exercise might be mediated by EGR-1/PTP1B signaling pathway in skeletal muscle, however further studies are necessary to confirm this mechanism.

The Caenorhabditis elegans protein SOC-3 permits an alternative mode of signal transduction by the EGL-15 FGF receptor

Fibroblast Growth Factors and their receptors (FGFRs) comprise a cell signaling module that can stimulate signaling by Ras and the kinases Raf, MEK, and ERK to regulate animal development and homeostatic functions. In Caenorhabditis elegans, the sole FGFR ortholog EGL-15 acts with the GRB2 ortholog SEM-5 to promote chemoattraction and migration by the sex myoblasts (SMs) and fluid homeostasis by the hypodermis (Hyp7). Cell-specific differences in EGL-15 signaling were suggested by the phenotypes caused by egl-15(n1457), an allele that removes a region of its C-terminal domain (CTD) known to bind SEM-5. To determine how mutations altered EGL-15 activity in the SMs and Hyp7, we used the kinase reporter ERK-KTR to measure activation of the ERK ortholog MPK-1. Consequences of egl-15(n1457) were cell-specific, resulting in loss of MPK-1 activity in the SMs and elevated activity in Hyp7. Previous studies of Hyp7 showed that loss of the CLR-1 phosphatase causes a fluid homeostasis defect termed "Clear" that is suppressed by reduction of EGL-15 signaling, a phenotype termed "Suppressor of Clear" (Soc). To identify mechanisms that permit EGL-15 signaling in Hyp7, we conducted a genetic screen for Soc mutants in the clr-1; egl-15(n1457) genotype. We report the identification of SOC-3, a protein with putative SEM-5-binding motifs and PH and PTB domains similar to DOK and IRS proteins. In combination with the egl-15(n1457) mutation, loss of either soc-3, the GAB1 ortholog soc-1, or the SHP2 ortholog ptp-2, reduced MPK-1 activation. We generated alleles of soc-3 to test the requirement for the SEM-5-binding motifs, finding that residue Tyr356 is required for function. We propose that EGL-15-mediated SM chemoattraction relies solely on the direct interaction between SEM-5 and the EGL-15 CTD. In Hyp7, EGL-15 signaling uses two mechanisms: the direct SEM-5 binding mechanism; and an alternative, CTD-independent mechanism involving SOC-3, SOC-1, and PTP-2. This work demonstrates that FGF signaling uses distinct, tissue-specific mechanisms in development, and identifies SOC-3 as a potential adaptor that facilitates Ras pathway activation by FGFR.

Catalytic activities of wild-type C. elegans DAF-2 kinase and dauer-associated mutants

DAF-2, the Caenorhabditis elegans insulin-like receptor homolog, regulates larval development, metabolism, stress response, and lifespan. The availability of numerous daf-2 mutant alleles has made it possible to elucidate the genetic mechanisms underlying these physiological processes. The DAF-2 pathway is significantly conserved with the human insulin/IGF-1 signaling pathway; it includes proteins homologous to human IRS, GRB-2, and PI3K, making it an important model to investigate human pathological conditions. We expressed and purified the kinase domain of wild-type DAF-2 to examine the catalytic activity and substrate specificity of the enzyme. Like the human insulin receptor kinase, DAF-2 kinase phosphorylates tyrosines within specific YxN or YxxM motifs, which are important for recruiting downstream effectors. DAF-2 kinase phosphorylated peptides derived from the YxxM and YxN motifs located in the C-terminal extension of the receptor tyrosine kinase, consistent with the idea that the DAF-2 receptor may possess independent signaling capacity. Unlike the human insulin or IGF-1 receptor kinases, DAF-2 kinase was poorly inhibited by the small-molecule inhibitor linsitinib. We also expressed and purified mutant kinases corresponding to daf-2 alleles that result in partial loss-of-function phenotypes in C. elegans. These mutations caused a complete loss of kinase function in vitro. Our biochemical investigations provide new insights into DAF-2 kinase function, and the approach should be useful for studying other mutations to shed light on DAF-2 signaling in C. elegans physiology.

iTRAQ proteomics analysis of placental tissue with gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus is an endocrine and metabolic disorder that appears for the first time during pregnancy and causes varying degrees of short- and/or long-term effects on the mother and child. The etiology of the disease is currently unknown and isobaric tags for relative and absolute quantitation proteomics approach, the present study attempted to identify potential proteins in placental tissues that may be involved in the pathogenesis of GDM and adverse foetal pregnancy outcomes.

METHODS

Pregnant women with GDM hospitalised were selected as the experimental group, and pregnant women with normal glucose metabolism as the control group. The iTRAQ protein quantification technology was used to screen the differentially expressed proteins between the GDM group and the normal control group, and the differentially expressed proteins were analysed by GO, KEGG, PPI, etc., and the key proteins were subsequently verified by western blot.

RESULTS

Based on the proteomics of iTRAQ, we experimented with three different samples of placental tissues from GDM and normal pregnant women, and the total number of identified proteins were 5906, 5959, and 6017, respectively, which were similar in the three different samples, indicating that the results were reliable. Through the Wayne diagram, we found that the total number of proteins coexisting in the three groups was 4475, and 91 differential proteins that could meet the quantification criteria were strictly screened, of which 32 proteins were up-regulated and 59 proteins were down-regulated. By GO enrichment analysis, these differential proteins are widely distributed in extracellular membrane-bounded organelle, mainly in extracellular exosome, followed by intracellular vesicle, extracellular organelle. It not only undertakes protein binding, protein complex binding, macromolecular complex binding, but also involves molecular biological functions such as neutrophil degranulation, multicellular organismal process, developmental process, cellular component organization, secretion, regulated exocytosis. Through the analysis of the KEGG signaling pathway, it is found that these differential proteins are mainly involved in HIF-1 signaling pathway, Glycolysis/Gluconeogenesis, Central carbon metabolism in cancer, AMPK signaling pathway, Proteoglycans in cancer, Protein processing in endoplasmic reticulum, Thyroid cancer, Alcoholism, Glucagon signaling pathway.

DISCUSSION

This preliminary study helps us to understand the changes in the placental proteome of GDM patients, and provides new insights into the pathophysiology of GDM.

CRK and NCK adaptors may functionally overlap in zebrafish neurodevelopment, as indicated by common binding partners and overlapping expression patterns

CRK adaptor proteins are important for signal transduction mechanisms driving cell proliferation and positioning during vertebrate central nervous system development. Zebrafish lacking both CRK family members exhibit small, disorganized retinas with 50% penetrance. The goal of this study was to determine whether another adaptor protein might functionally compensate for the loss of CRK adaptors. Expression patterns in developing zebrafish, and bioinformatic analyses of the motifs recognized by their SH2 and SH3 domains, suggest NCK adaptors are well-positioned to compensate for loss of CRK adaptors. In support of this hypothesis, proteomic analyses found CRK and NCK adaptors share overlapping interacting partners including known regulators of cell adhesion and migration, suggesting their functional intersection in neurodevelopment.

CD248 promotes insulin resistance by binding to the insulin receptor and dampening its insulin-induced autophosphorylation

BACKGROUND

In spite of new treatments, the incidence of type 2 diabetes (T2D) and its morbidities continue to rise. The key feature of T2D is resistance of adipose tissue and other organs to insulin. Approaches to overcome insulin resistance are limited due to a poor understanding of the mechanisms and inaccessibility of drugs to relevant intracellular targets. We previously showed in mice and humans that CD248, a pre/adipocyte cell surface glycoprotein, acts as an adipose tissue sensor that mediates the transition from healthy to unhealthy adipose, thus promoting insulin resistance.

METHODS

Molecular mechanisms by which CD248 regulates insulin signaling were explored using in vivo insulin clamp studies and biochemical analyses of cells/tissues from CD248 knockout (KO) and wild-type (WT) mice with diet-induced insulin resistance. Findings were validated with human adipose tissue specimens.

FINDINGS

Genetic deletion of CD248 in mice, overcame diet-induced insulin resistance with improvements in glucose uptake and lipolysis in white adipose tissue depots, effects paralleled by increased adipose/adipocyte GLUT4, phosphorylated AKT and GSK3β, and reduced ATGL. The insulin resistance of the WT mice could be attributed to direct interaction of the extracellular domains of CD248 and the insulin receptor (IR), with CD248 acting to block insulin binding to the IR. This resulted in dampened insulin-mediated autophosphorylation of the IR, with reduced downstream signaling/activation of intracellular events necessary for glucose and lipid homeostasis.

INTERPRETATION

Our discovery of a cell-surface CD248-IR complex that is accessible to pharmacologic intervention, opens research avenues toward development of new agents to prevent/reverse insulin resistance.

FUNDING

Funded by Canadian Institutes of Health Research (CIHR), Natural Sciences and Engineering Research Council of Canada (NSERC), Canada Foundations for Innovation (CFI), the Swedish Diabetes Foundation, Family Ernfors Foundation and Novo Nordisk Foundation.

The Impact of ETV6-NTRK3 Oncogenic Gene Fusions on Molecular and Signaling Pathway Alterations

Chromosomal translocations creating fusion genes are common cancer drivers. The oncogenic ETV6-NTRK3 (EN) gene fusion joins the sterile alpha domain of the ETV6 transcription factor with the tyrosine kinase domain of the neurotrophin-3 receptor NTRK3. Four EN variants with alternating break points have since been detected in a wide range of human cancers. To provide molecular level insight into EN oncogenesis, we employed a proximity labeling mass spectrometry approach to define the molecular context of the fusions. We identify in total 237 high-confidence interactors, which link EN fusions to several key signaling pathways, including ERBB, insulin and JAK/STAT. We then assessed the effects of EN variants on these pathways, and showed that the pan NTRK inhibitor Selitrectinib (LOXO-195) inhibits the oncogenic activity of EN2, the most common variant. This systems-level analysis defines the molecular framework in which EN oncofusions operate to promote cancer and provides some mechanisms for therapeutics.

OVEREXPRESSION OF PTEN GENE INCREASES INS2 GENE MRNA EXPRESSION, NOT INS1 GENE MRNA EXPRESSION, IN INSULINOMA CELL LINE RIN-5F

Objective

One functional neuroendocrine tumor that causes hypoglycemia due to inappropriately high insulin production is an insulinoma. In rats, two genes coding for insulin, insulin 1 (Ins1) and insulin 2 (Ins2) are found on chromosome 1. Ins1 was produced from an Ins2 transcript, and it was inserted into the genome via an RNA-mediated duplication-transposition event, according to some structural feature analyses.

Methods

In this study, the author has looked at how overexpression of the PTEN gene in the insulinoma cell line Rin-5F affects the expression of the insulin genes, Ins 1 and Ins 2.

Results

In the insulinoma cell line, overexpression of the PTEN gene boosts Ins2 gene mRNA expression but not Ins1 gene mRNA expression. It has been reported that PTEN upregulates insulin signaling by increasing insulin receptor substrate (IRS)-2 mRNA levels. Also, PTEN has been reported to be secreted in exosomes and thereafter, into extracellular space.

Conclusions

The present study suggested that overexpression of PTEN might induce the increasing Ins 2 gene expression, one of the phosphorylated genes against the IRS-2 through the insulin/IGF-1 receptor. Our knowledge of the molecular pathways of PTEN relating the synthesis of insulin has been increased by the present study.

γ-glutamylcysteine alleviates insulin resistance and hepatic steatosis by regulating adenylate cyclase and IGF-1R/IRS1/PI3K/Akt signaling pathways

Type 2 diabetes mellitus (T2DM), a complex metabolism disease, which was characterized by metabolic disorders including hyperglycemia, has become a major health problem due to the increasing prevalence worldwide. γ-glutamylcysteine (γ-GC) as an immediate precursor of glutathione (GSH) was originally used for the treatment of sepsis, inflammation bowel disease, and senescence. Here, we evaluated the capacity of γ-GC on diabetes-related metabolic parameters in db/db mice and insulin resistance (IR) amelioration in cells induced by palmitic acid (PA). Our data suggested that γ-GC treatment decreased body weight, reduced adipose tissue size, ameliorated ectopic fat deposition in liver, increased the GSH content in liver, improved glucose control and other diabetes-related metabolic parameters in vivo. Moreover, in vitro experiments showed that γ-GC could maintain the balance of free fatty acids (FFAs) and glucose uptake through regulating the translocation of CD36 and GLUT4 from cytoplasm to plasma membrane. Furthermore, our finding also provided evidence that γ-GC could activate Akt not only via adenylate cyclase (AC)/cAMP/PI3K signaling pathway, but also via IGF-1R/IRS1/PI3K signaling pathway to improve IR and hepatic steatosis. Blocking either of two signaling pathways could not activate Akt activation induced by γ-GC. This unique characteristic ensures the important role of γ-GC in glucose metabolism. Collectively, these results suggested that γ-GC could serve as a candidate dipeptide for the treatment of T2DM and related chronic diabetic complications via activating AC and IGF-1R/IRS1/PI3K/Akt signaling pathways to regulate CD36 and GLUT4 trafficking.

Molecular Mechanisms for the Vicious Cycle between Insulin Resistance and the Inflammatory Response in Obesity

The comprehensive anabolic effects of insulin throughout the body, in addition to the control of glycemia, include ensuring lipid homeostasis and anti-inflammatory modulation, especially in adipose tissue (AT). The prevalence of obesity, defined as a body mass index (BMI) ≥ 30 kg/m², has been increasing worldwide on a pandemic scale with accompanying syndemic health problems, including glucose intolerance, insulin resistance (IR), and diabetes. Impaired tissue sensitivity to insulin or IR paradoxically leads to diseases with an inflammatory component despite hyperinsulinemia. Therefore, an excess of visceral AT in obesity initiates chronic low-grade inflammatory conditions that interfere with insulin signaling via insulin receptors (INSRs). Moreover, in response to IR, hyperglycemia itself stimulates a primarily defensive inflammatory response associated with the subsequent release of numerous inflammatory cytokines and a real threat of organ function deterioration. In this review, all components of this vicious cycle are characterized with particular emphasis on the interplay between insulin signaling and both the innate and adaptive immune responses related to obesity. Increased visceral AT accumulation in obesity should be considered the main environmental factor responsible for the disruption in the epigenetic regulatory mechanisms in the immune system, resulting in autoimmunity and inflammation.

Setting sail: Maneuvering SHP2 activity and its effects in cancer

Since the discovery of tyrosine phosphorylation being a critical modulator of cancer signaling, proteins regulating phosphotyrosine levels in cells have fast become targets of therapeutic intervention. The nonreceptor protein tyrosine phosphatase (PTP) coded by the PTPN11 gene "SHP2" integrates phosphotyrosine signaling from growth factor receptors into the RAS/RAF/ERK pathway and is centrally positioned in processes regulating cell development and oncogenic transformation. Dysregulation of SHP2 expression or activity is linked to tumorigenesis and developmental defects. Even as a compelling anti-cancer target, SHP2 was considered "undruggable" for a long time owing to its conserved catalytic PTP domain that evaded drug development. Recently, SHP2 has risen from the "undruggable curse" with the discovery of small molecules that manipulate its intrinsic allostery for effective inhibition. SHP2's unique domain arrangement and conformation(s) allow for a truly novel paradigm of inhibitor development relying on skillful targeting of noncatalytic sites on proteins. In this review we summarize the biological functions, signaling properties, structural attributes, allostery and inhibitors of SHP2.

Expression of IRS2 in the female reproductive system during the estrous cycle in mice

Insulin receptor substrate 2 (IRS2) participates in reproduction; however, the location and expression of IRS2 in the reproductive system of female mice is not clear. We used real-time quantitative polymerase chain reaction (RT-PCR), western blot and immunohistochemical staining to investigate the expression of IRS2 in the ovary, oviduct and uterus of female mice during the estrous cycle. We found that IRS2 was expressed in all reproductive organs of mouse and that the expression level changed with the estrous phases. The expression of IRS2 in reproductive organs was greatest during estrus.

Hypoglycemic Potential of Carica papaya in Liver Is Mediated through IRS-2/PI3K/SREBP-1c/GLUT2 Signaling in High-Fat-Diet-Induced Type-2 Diabetic Male Rats

Regardless of socioeconomic or demographic background, the prevalence of type 2 diabetes mellitus, which affects more than half a billion people worldwide, has been steadily increasing over time. The health, emotional, sociological, and economic well-being of people would suffer if this number is not successfully handled. The liver is one of the key organs accountable for sustaining metabolic balance. Elevated levels of reactive oxygen species inhibit the recruitment and activation of IRS-1, IRS-2, and PI3K-Akt downstream signaling cascade. These signaling mechanisms reduce hepatic glucose absorption and glycogenesis while increasing hepatic glucose output and glycogenolysis. In our work, an analysis of the molecular mechanism of Carica papaya in mitigating hepatic insulin resistance in vivo and in silico was carried out. The gluconeogenic enzymes, glycolytic enzymes, hepatic glycogen tissue concentration, oxidative stress markers, enzymatic antioxidants, protein expression of IRS-2, PI3K, SREBP-1C, and GLUT-2 were evaluated in the liver tissues of high-fat-diet streptozotocin-induced type 2 diabetic rats using q-RT-PCR as well as immunohistochemistry and histopathology. Upon treatment, C. papaya restored the protein and gene expression in the liver. In the docking analysis, quercetin, kaempferol, caffeic acid, and p-coumaric acid present in the extract were found to have high binding affinities against IRS-2, PI3K, SREBP-1c, and GLUT-2, which may have contributed much to the antidiabetic property of C. papaya. Thus, C. papaya was capable of restoring the altered levels in the hepatic tissues of T2DM rats, reversing hepatic insulin resistance.

Arsenic induces the global hypophosphorylation of insulin receptor substrate proteins in differentiated human neuroblastoma SH-SY5Y cells

We recently reported that arsenic disrupted neuronal insulin signaling. Here, we further investigated the effect of arsenic on insulin receptor substrate (IRS) proteins, which are crucial downstream signaling molecules of insulin in differentiated human neuroblastoma SH-SY5Y cells. We also found that prolonged arsenic treatment accelerated the migration of IRS1 and IRS2 on SDS-PAGE. Treatment with phosphatases abolished the arsenic-induced increased mobility of IRS, suggesting that the electrophoretic mobility shift of IRS on SDS-PAGE by arsenic was phosphorylation-dependent. By using label-free mass spectrometry, the phosphorylation sites of IRS1 were found to be S24, S345, S636, T774, S1057, S1058, and S1070, while those of IRS2 were at S645, Y653, T657, S665, S667, S669, S672, S915, and S1203, which were at least 2-fold lower than found in the control. These findings indicated a global hypophosphorylation of IRS proteins after prolonged arsenic treatment. In addition, four novel phosphorylation sites were identified on IRS1 (T774, S1057, S1058, and S1070), with another two on IRS2 (S665 and S667). As basal IRS phosphorylation plays an important role in insulin signaling, the reduction of IRS phosphorylation on multiple residues may underlie arsenic-impaired insulin signaling in neurons.

Evaluation of affinity-purification coupled to mass spectrometry approaches for capture of short linear motif-based interactions

Low affinity and transient protein-protein interactions, such as short linear motif (SLiM)-based interactions, require dedicated experimental tools for discovery and validation. Here, we evaluated and compared biotinylated peptide pulldown and protein interaction screen on peptide matrix (PRISMA) coupled to mass-spectrometry (MS) using a set of peptides containing interaction motifs. Eight different peptide sequences that engage in interactions with three distinct protein domains (KEAP1 Kelch, MDM2 SWIB, and TSG101 UEV) with a wide range of affinities were tested. We found that peptide pulldown can be an effective approach for SLiM validation, however, parameters such as protein abundance and competitive interactions can prevent the capture of known interactors. The use of tandem peptide repeats improved the capture and preservation of some interactions. When testing PRISMA, it failed to provide comparable results for model peptides that successfully pulled down known interactors using biotinylated peptide pulldown. Overall, in our hands, we find that albeit more laborious, biotin-peptide pulldown was more successful in terms of validation of known interactions. Our results highlight that the tested affinity-capture MS-based methods for validation of SLiM-based interactions from cell lysates are suboptimal, and we identified parameters for consideration for method development.

Cell cycle control by the insulin-like growth factor signal: at the crossroad between cell growth and mitotic regulation

In proliferating cells and tissues a number of checkpoints (G1/S and G2/M) preceding cell division (M-phase) require the signal provided by growth factors present in serum. IGFs (I and II) have been demonstrated to constitute key intrinsic components of the peptidic active fraction of mammalian serum. In vivo genetic ablation studies have shown that the cellular signal triggered by the IGFs through their cellular receptors represents a non-replaceable requirement for cell growth and cell cycle progression. Retroactive and current evaluation of published literature sheds light on the intracellular circuitry activated by these factors providing us with a better picture of the pleiotropic mechanistic actions by which IGFs regulate both cell size and mitogenesis under developmental growth as well as in malignant proliferation. The present work aims to summarize the cumulative knowledge learned from the IGF ligands/receptors and their intracellular signaling transducers towards control of cell size and cell-cycle with particular focus to their actionable circuits in human cancer. Furthermore, we bring novel perspectives on key functional discriminants of the IGF growth-mitogenic pathway allowing re-evaluation on some of its signal components based upon established evidences.

Altered macronutrient composition and genetics influence the complex transcriptional network associated with adiposity in the Collaborative Cross

Background

Obesity is a serious disease with a complex etiology characterized by overaccumulation of adiposity resulting in detrimental health outcomes. Given the liver’s critical role in the biological processes that attenuate adiposity accumulation, elucidating the influence of genetics and dietary patterns on hepatic gene expression is fundamental for improving methods of obesity prevention and treatment. To determine how genetics and diet impact obesity development, mice from 22 strains of the genetically diverse recombinant inbred Collaborative Cross (CC) mouse panel were challenged to either a high-protein or high-fat high-sucrose diet, followed by extensive phenotyping and analysis of hepatic gene expression.

Results

Over 1000 genes differentially expressed by perturbed dietary macronutrient composition were enriched for biological processes related to metabolic pathways. Additionally, over 9000 genes were differentially expressed by strain and enriched for biological process involved in cell adhesion and signaling. Weighted gene co-expression network analysis identified multiple gene clusters (modules) associated with body fat % whose average expression levels were influenced by both dietary macronutrient composition and genetics. Each module was enriched for distinct types of biological functions.

Conclusions

Genetic background affected hepatic gene expression in the CC overall, but diet macronutrient differences also altered expression of a specific subset of genes. Changes in macronutrient composition altered gene expression related to metabolic processes, while genetic background heavily influenced a broad range of cellular functions and processes irrespective of adiposity. Understanding the individual role of macronutrient composition, genetics, and their interaction is critical to developing therapeutic strategies and policy recommendations for precision nutrition.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12263-022-00714-x.

A comprehensive review of SHP2 and its role in cancer

Src homology 2-containing protein tyrosine phosphatase 2 (SHP2) is a non-receptor protein tyrosine phosphatase ubiquitously expressed mainly in the cytoplasm of several tissues. SHP2 modulates diverse cell signaling events that control metabolism, cell growth, differentiation, cell migration, transcription and oncogenic transformation. It interacts with diverse molecules in the cell, and regulates key signaling events including RAS/ERK, PI3K/AKT, JAK/STAT and PD-1 pathways downstream of several receptor tyrosine kinases (RTKs) upon stimulation by growth factors and cytokines. SHP2 acts as both a phosphatase and a scaffold, and plays prominently oncogenic functions but can be tumor suppressor in a context-dependent manner. It typically acts as a positive regulator of RTKs signaling with some inhibitory functions reported as well. SHP2 expression and activity is regulated by such factors as allosteric autoinhibition, microRNAs, ubiquitination and SUMOylation. Dysregulation of SHP2 expression or activity causes many developmental diseases, and hematological and solid tumors. Moreover, upregulated SHP2 expression or activity also decreases sensitivity of cancer cells to anticancer drugs. SHP2 is now considered as a compelling anticancer drug target and several classes of SHP2 inhibitors with different mode of action are developed with some already in clinical trial phases. Moreover, novel SHP2 substrates and functions are rapidly growing both in cell and cancer. In view of this, we comprehensively and thoroughly reviewed literatures about SHP2 regulatory mechanisms, substrates and binding partners, biological functions, roles in human cancers, and different classes of small molecule inhibitors target this oncoprotein in cancer.

The Role of Insulin Receptor Substrate Proteins in Bronchopulmonary Dysplasia and Asthma: New Potential Perspectives

Insulin receptor substrates (IRSs) are proteins that are involved in signaling through the insulin receptor (IR) and insulin-like growth factor (IGFR). They can also interact with other receptors including growth factor receptors. Thus, they represent a critical node for the transduction and regulation of multiple signaling pathways in response to extracellular stimuli. In addition, IRSs play a central role in processes such as inflammation, growth, metabolism, and proliferation. Previous studies have highlighted the role of IRS proteins in lung diseases, in particular asthma. Further, the members of the IRS family are the common proteins of the insulin growth factor signaling cascade involved in lung development and disrupted in bronchopulmonary dysplasia (BPD). However, there is no study focusing on the relationship between IRS proteins and BPD yet. Unfortunately, there is still a significant gap in knowledge in this field. Thus, in this review, we aimed to summarize the current knowledge with the major goal of exploring the possible roles of IRS in BPD and asthma to foster new perspectives for further investigations.

The insulin receptor family in the heart: new light on old insights

Insulin was discovered over 100 years ago. Whilst the first half century defined many of the physiological effects of insulin, the second emphasised the mechanisms by which it elicits these effects, implicating a vast array of G proteins and their regulators, lipid and protein kinases and counteracting phosphatases, and more. Potential growth-promoting and protective effects of insulin on the heart emerged from studies of carbohydrate metabolism in the 1960s, but the insulin receptors (and the related receptor for insulin-like growth factors 1 and 2) were not defined until the 1980s. A related third receptor, the insulin receptor-related receptor remained an orphan receptor for many years until it was identified as an alkali-sensor. The mechanisms by which these receptors and the plethora of downstream signalling molecules confer cardioprotection remain elusive. Here, we review important aspects of the effects of the three insulin receptor family members in the heart. Metabolic studies are set in the context of what is now known of insulin receptor family signalling and the role of protein kinase B (PKB or Akt), and the relationship between this and cardiomyocyte survival versus death is discussed. PKB/Akt phosphorylates numerous substrates with potential for cardioprotection in the contractile cardiomyocytes and cardiac non-myocytes. Our overall conclusion is that the effects of insulin on glucose metabolism that were initially identified remain highly pertinent in managing cardiomyocyte energetics and preservation of function. This alone provides a high level of cardioprotection in the face of pathophysiological stressors such as ischaemia and myocardial infarction.

A brief review of vitamin D as a potential target for the regulation of blood glucose and inflammation in diabetes-associated periodontitis

Diabetes is a metabolic disorder associated with various complications, including periodontitis. The risk of periodontitis is increased in patients with diabetes, while vitamin D deficiency is associated with both diabetes and periodontitis. Thus, there is a need to identify the molecular effects of vitamin D on the regulation of inflammation and glucose in diabetes-associated periodontitis. The Web of Science, Scopus, and PubMed databases were searched for studies of the molecular effects of vitamin D. Molecular effects were reportedly mediated by salivary secretions, interactions of advanced glycation end products (AGEs) with receptors of AGEs (RAGEs), cytokines, and oxidative stress pathways linking diabetes with periodontitis. Vitamin D supplementation attenuates inflammation in diabetes-associated periodontitis by reducing the levels of inflammatory cytokines and numbers of immune cells; it also has antibacterial effects. Vitamin D reduces cytokine levels through regulation of the extracellular signal-related kinase 1/2 and Toll-like receptor 1/2 pathways, along with the suppression of interleukin expression. Glucose homeostasis is altered in diabetes either because of reduced insulin production or decreased insulin sensitivity. These vitamin D-related alterations of glucoregulatory factors may contribute to hyperglycaemia; hyperglycaemia may also lead to alterations of glucoregulatory factors. This review discusses the pathways involved in glucose regulation and effects of vitamin D supplementation on glucose regulation. Further studies are needed to characterise the effects of vitamin D on diabetes-associated periodontitis.

Single-molecule studies reveal regulatory interactions between master kinases PDK1, AKT1, and PKC

Leukocyte migration is controlled by a leading-edge chemosensory pathway that generates the regulatory lipid phosphatidylinositol-3,4,5-trisphosphate (PIP₃), a growth signal, thereby driving leading-edge expansion up attractant gradients toward sites of infection, inflammation, or tissue damage. PIP₃ also serves as an important growth signal in growing cells and oncogenesis. The kinases PDK1, AKT1 or PKB, and PKCα are key components of a plasma-membrane-based PIP₃ and Ca²⁺ signaling circuit that regulates these processes. PDK1 and AKT1 are recruited to the membrane by PIP₃, whereas PKCα is recruited to the membrane by Ca²⁺. All three of these master kinases phosphoregulate an array of protein targets. For example, PDK1 activates AKT1, PKCα, and other AGC kinases by phosphorylation at key sites. PDK1 is believed to form PDK1-AKT1 and PDK1-PKCα heterodimers stabilized by a PDK1-interacting fragment (PIF) interaction between the PDK1 PIF pocket and the PIF motif of the AGC binding partner. Here, we present the first, to our knowledge, single-molecule studies of full-length PDK1 and AKT1 on target membrane surfaces, as well as their interaction with full-length PKCα. These studies directly detect membrane-bound PDK1-AKT1 and PDK1-PKCα heterodimers stabilized by PIF interactions formed at physiological ligand concentrations. PKCα exhibits eightfold higher PDK1 affinity than AKT1 and can competitively displace AKT1 from PDK1-AKT1 heterodimers. Ensemble activity measurements under matched conditions reveal that PDK1 activates AKT1 via a cis mechanism by phosphorylating an AKT1 molecule in the same PDK1-AKT1 heterodimer, whereas PKCα acts as a competitive inhibitor of this phosphoactivation reaction by displacing AKT1 from PDK1. Overall, the findings provide insights into the binding and regulatory interactions of the three master kinases on their target membrane and suggest that a recently described tumor suppressor activity of PKC isoforms may arise from its ability to downregulate PDK1-AKT1 phosphoactivation in the PIP₃-PDK1-AKT1-mTOR pathway linked to cell growth and oncogenesis.

Differential involvement of insulin receptor substrate (IRS)-1 and IRS-2 in brain insulin signaling is associated with the effects on amyloid pathology in a mouse model of Alzheimer's disease

Insulin signaling has been implicated in the metabolism as well as aging and longevity. Type 2 diabetes mellitus and its core pathology, insulin resistance, has also been implicated in the development of Alzheimer's disease (AD) and amyloid-β deposition in humans. By contrast, genetic ablation of the insulin/IGF-1 signaling (IIS) pathway components, e.g. insulin receptor substrate (IRS)-2, has been documented to suppress amyloid-β accumulation in the brains of transgenic mice overexpressing AD mutant β-amyloid precursor protein (APP). Therefore, the brain IIS may be a key modifiable molecular target in the pathophysiology of AD. IRS-1 and IRS-2 are critical nodes in IIS as substrates for insulin receptor and IGF-1 receptor, although the functional differences between IRS-1 and IRS-2 in the adult brain are yet to be explored. To examine their relative contribution to the brain IIS activity and AD pathomechanism, we generated APP transgenic mice lacking either IRS-1 or IRS-2. IRS-1 deficiency had little effects on the brain IIS pathway associated with compensatory activation of IRS-2, whereas IRS-2 deficiency was not fully compensated by activation of IRS-1, and the downstream activation of Akt also was significantly compromised. Pathological analyses of the cortical tissues showed that the biochemical levels of soluble and insoluble amyloid-β, the amyloid-β histopathology, and tau phosphorylation were not affected by the absence of IRS-1, in contrast to the marked alteration in IRS-2 deleted mice. These results suggest the predominance of IRS-2 in the brain IIS, and support the hypothesis that reduced IIS exerts anti-amyloid effects in the brain.

Drugs Interfering with Insulin Resistance and Their Influence on the Associated Hypermetabolic State in Severe Burns: A Narrative Review

It has become widely accepted that insulin resistance and glucose hypermetabolism can be linked to acute pathologies, such as burn injury, severe trauma, or sepsis. Severe burns can determine a significant increase in catabolism, having an important effect on glucose metabolism and on muscle protein metabolism. It is imperative to acknowledge that these alterations can lead to increased mortality through organ failure, even when the patients survive the initial trauma caused by the burn. By limiting the peripheral use of glucose with consequent hyperglycemia, insulin resistance determines compensatory increased levels of insulin in plasma. However, the significant alterations in cellular metabolism lead to a lack of response to insulin's anabolic functions, as well as to a decrease in its cytoprotective role. In the end, via pathological insulin signaling associated with increased liver gluconeogenesis, elevated levels of glucose are detected in the blood. Several cellular mechanisms have been incriminated in the development of insulin resistance in burns. In this context, the main aim of this review article is to summarize some of the drugs that might interfere with insulin resistance in burns, taking into consideration that such an approach can significantly improve the prognosis of the burned patient.

The Interactions of Insulin and Vitamin A Signaling Systems for the Regulation of Hepatic Glucose and Lipid Metabolism

The pandemics of obesity and type 2 diabetes have become a concern of public health. Nutrition plays a key role in these concerns. Insulin as an anabolic hormonal was discovered exactly 100 years ago due to its activity in controlling blood glucose level. Vitamin A (VA), a lipophilic micronutrient, has been shown to regulate glucose and fat metabolism. VA's physiological roles are mainly mediated by its metabolite, retinoic acid (RA), which activates retinoic acid receptors (RARs) and retinoid X receptors (RXRs), which are two transcription factors. The VA status and activations of RARs and RXRs by RA and synthetic agonists have shown to affect the glucose and lipid metabolism in animal models. Both insulin and RA signaling systems regulate the expression levels of genes involved in the regulation of hepatic glucose and lipid metabolism. Interactions of insulin and RA signaling systems have been observed. This review is aimed at summarizing the history of diabetes, insulin and VA signaling systems; the effects of VA status and activation of RARs and RXRs on metabolism and RAR and RXR phosphorylation; and possible interactions of insulin and RA in the regulation of hepatic genes for glucose and lipid metabolism. In addition, some future research perspectives for understanding of nutrient and hormone interactions are provided.

The insulin receptor family and protein kinase B (Akt) are activated in the heart by alkaline pH and α1-adrenergic receptors

Insulin and insulin-like growth factor stimulate protein synthesis and cardioprotection in the heart, acting through their receptors (INSRs, IGF1Rs) and signalling via protein kinase B (PKB, also known as Akt). Protein synthesis is increased in hearts perfused at alkaline pH_o to the same extent as with insulin. Moreover, α₁-adrenergic receptor (α₁-AR) agonists (e.g. phenylephrine) increase protein synthesis in cardiomyocytes, activating PKB/Akt. In both cases, the mechanisms are not understood. Our aim was to determine if insulin receptor-related receptors (INSRRs, activated in kidney by alkaline pH) may account for the effects of alkaline pH_o on cardiac protein synthesis, and establish if α₁-ARs signal through the insulin receptor family. Alkaline pH_o activated PKB/Akt signalling to the same degree as insulin in perfused adult male rat hearts. INSRRs were expressed in rat hearts and, by immunoblotting for phosphorylation (activation) of INSRRs/INSRs/IGF1Rs, we established that INSRRs, together with INSRs/IGF1Rs, are activated by alkaline pH_o. The INSRR/INSR/IGF1R kinase inhibitor, linsitinib, prevented PKB/Akt activation by alkaline pH_o, indicating that INSRRs/INSRs/IGF1Rs are required. Activation of PKB/Akt in cardiomyocytes by α₁-AR agonists was also inhibited by linsitinib. Furthermore, linsitinib inhibited cardiomyocyte hypertrophy induced by α₁-ARs in cultured cells, reduced the initial cardiac adaptation (24 h) to phenylephrine in vivo (assessed by echocardiography) and increased cardiac fibrosis over 4 days. We conclude that INSRRs are expressed in the heart and, together with INSRs/IGF1Rs, the insulin receptor family provide a potent system for promoting protein synthesis and cardioprotection. Moreover, this system is required for adaptive hypertrophy induced by α₁-ARs.

Diversity of insulin and IGF signaling in breast cancer: Implications for therapy

This review highlights the significance of the insulin receptor (IR) and insulin-like growth factor-1 receptor (IGF-1R) signaling pathway in cancer and assesses its potential as a therapeutic target. Our emphasis is on breast cancer, but this pathway is central to the behavior of many cancers. An understanding of how IR/IGF-1R signaling contributes to the function of the normal mammary gland provides a foundation for understanding its aberrations in breast cancer. Specifically, dysregulation of the expression and function of ligands (insulin, IGF-1 and IGF-2), receptors and their downstream signaling effectors drive breast cancer initiation and progression, often in a subtype-dependent manner. Efforts to target this pathway for the treatment of cancer have been hindered by several factors including a lack of biomarkers to select patients that could respond to targeted therapy and adverse effects on normal metabolism. To this end, we discuss ongoing efforts aimed at overcoming such obstacles.

Quantitative phosphoproteomic analysis of IRS1 in skeletal muscle from men with normal glucose tolerance or type 2 diabetes: A case-control study

BACKGROUND & AIMS

The physiological regulation and contribution of the multiple phosphorylation sites of insulin receptor substrate 1 (IRS1) to the pathogenesis of insulin resistance is unknown. Our aims were to map the phosphorylated motifs of IRS1 in skeletal muscle from people with normal glucose tolerance (NGT; n = 11) or type 2 diabetes mellitus (T2DM; n = 11).

METHODS

Skeletal muscle biopsies were obtained under fasted conditions or during a euglycemic clamp and IRS1 phosphorylation sites were identified by mass spectrometry.

RESULTS

We identified 33 phosphorylation sites in biopsies from fasted individuals, including 2 previously unreported sites ([Ser393] and [Thr1017]). In men with NGT and T2DM, insulin increased phosphorylation of 5 peptides covering 10 serine or threonine sites and decreased phosphorylation of 6 peptides covering 9 serine, threonine or tyrosine sites. Insulin-stimulation increased phosphorylation of 2 peptides, and decreased phosphorylation of 2 peptides only in men with NGT. Insulin increased phosphorylation of 2 peptides only in men with T2DM.

CONCLUSIONS

Despite severe skeletal muscle insulin resistance, the pattern of IRS1 phosphorylation was not uniformly altered in T2DM. Our results contribute to the evolving understanding of the physiological regulation of insulin signaling and complement the comprehensive map of IRS1 phosphorylation in T2DM.

Insulin-like growth factor 1 of wild vertebrates in a life-history context

Broad variation in intra- and interspecific life-history traits is largely shaped by resource limitation and the ensuing allocation trade-offs that animals are forced to make. Insulin-like growth factor 1 (IGF-1), a growth-hormone-dependent peptide, may be a key player in the regulation of allocation processes. In laboratory animals, the effects of IGF-1 on growth- and development (positive), reproduction (positive), and longevity (negative) are well established. We here review the evidence on these effects in wild vertebrates, where animals are more likely to face resource limitation and other challenges. We point out the similarities and dissimilarities in patterns of IGF-1 functions obtained in these two different study settings and discuss the knowledge we need to develop a comprehensive picture of the role of IGF-1 in mediating life-history variation of wild vertebrates.

AAV delivery of shRNA against IRS1 in GABAergic neurons in rat hippocampus impairs spatial memory in females and male rats

Brain insulin resistance is a major factor leading to impaired cognitive function and it is considered as the onset of Alzheimer´s disease. Insulin resistance is intimately linked to inflammatory conditions, many studies have revealed how pro-inflammatory cytokines lead to insulin resistance, by inhibiting IRS1 function. Thus, the dysfunction of insulin signaling is concomitant with inflammatory biomarkers. However, the specific effect of IRS1 impaired function in otherwise healthy brain has not been dissected out. So, we decided in our study, to study the specific role of IRS1 in the hippocampus, in the absence of comorbidities. To that end, shRNA against rat and human IRS1 was designed and tested in cultured HEK cells to evaluate mRNA levels and specificity. The best candidate sequence was encapsulated in an AAV vector (strain DJ8) under the control of the cytomegalovirus promoter and together with the green fluorescent protein gene as a reporter. AAV-CMV-shIRS1-EGFP and control AAV-CMV-EGFP were inoculated into the dorsal hippocampus of female and male Wistar rats. One month later, animals undertook a battery of behavioral paradigms evaluating spatial and social memory and anxiety. Our results suggest that females displayed increased susceptibility to AAV-shIRS1 in the novel recognition object paradigm; whereas both females and males show impaired performance in the T maze when infected with AAV-shIRS1 compared to control. Anxiety parameters were not affected by AAV-shIRS1 infection. We observed specific fluorescence within the hilum of the dentate gyrus, in immuno-characterized parvalbumin and somatostatin neurons. AAV DJ8 did not enter astrocytes. Intense green fibers were found in the fornix, mammillary bodies, and in the medial septum indicating that hippocampal efferent had been efficiently targeted by the AAV DJ8 infection. We observed that AAV-shIRS1 reduced significantly synaptophysin labeling in hippocampal-septal projections compared to controls. These results support that, small alterations in the insulin/IGF1 pathway in specific hippocampal circuitries can underlie alterations in synaptic plasticity and affect behavior, in the absence of inflammatory conditions.

Understanding IGF-II Action through Insights into Receptor Binding and Activation

The insulin-like growth factor (IGF) system regulates metabolic and mitogenic signaling through an intricate network of related receptors and hormones. IGF-II is one of several hormones within this system that primarily regulates mitogenic functions and is especially important during fetal growth and development. IGF-II is also found to be overexpressed in several cancer types, promoting growth and survival. It is also unique in the IGF system as it acts through both IGF-1R and insulin receptor isoform A (IR-A). Despite this, IGF-II is the least investigated ligand of the IGF system. This review will explore recent developments in IGF-II research including a structure of IGF-II bound to IGF-1R determined using cryo-electron microscopy (cryoEM). Comparisons are made with the structures of insulin and IGF-I bound to their cognate receptors. Finally discussed are outstanding questions in the mechanism of action of IGF-II with the goal of developing antagonists of IGF action in cancer.

Can antioxidants be effective therapeutics for type 2 diabetes?

The global obesity epidemic and the growing elderly population largely contribute to the increasing incidence of type 2 diabetes. Insulin resistance acts as a critical link between the present obesity pandemic and type 2 diabetes. Naturally occurring reactive oxygen species (ROS) regulate intracellular signaling and are kept in balance by the antioxidant system. However, the imbalance between ROS production and antioxidant capacity causes ROS accumulation and induces oxidative stress. Oxidative stress interrupts insulin-mediated intracellular signaling pathways, as supported by studies involving genetic modification of antioxidant enzymes in experimental rodents. In addition, a close association between oxidative stress and insulin resistance has been reported in numerous human studies. However, the controversial results with the use of antioxidants in type 2 diabetes raise the question of whether oxidative stress plays a critical role in insulin resistance. In this review article, we discuss the relevance of oxidative stress to insulin resistance based on genetically modified animal models and human trials.

Growth Factors, and Cytokines; Understanding the Role of Tyrosine Phosphatase SHP2 in Gametogenesis and Early Embryo Development

Growth factors and cytokines have vital roles in germ cell development, gamete maturation, and early embryo development. Cell surface receptors are present for growth factors and cytokines to integrate with and trigger protein signaling in the germ and embryo intracellular milieu. Src-homology-2-containing phosphotyrosine phosphatase (SHP2) is a ubiquitously expressed, multifunctional protein that plays a central role in the signaling pathways involved in growth factor receptors, cytokine receptors, integrins, and G protein-coupled receptors. Over recent decades, researchers have recapitulated the protein signaling networks that influence gamete progenitor specification as well as gamete differentiation and maturation. SHP2 plays an indispensable role in cellular growth, survival, proliferation, differentiation, and migration, as well as the basic events in gametogenesis and early embryo development. SHP2, a classic cytosolic protein and a key regulator of signal transduction, displays unconventional nuclear expression in the genital organs. Several observations provided shreds of evidence that this behavior is essential for fertility. The growth factor and cytokine-dependent roles of SHP2 and its nuclear/cytoplasmic presence during gamete maturation, early embryonic development and embryo implantation are fascinating and complex subjects. This review is intended to summarize the previous and recent knowledge about the SHP2 functions in gametogenesis and early embryo development.

Polymorphism analysis of the Gly972Arg IRS-1 and Gly1057Asp IRS-2 genes in obese pregnant women

Genes encoding insulin receptor substrates IRS-1 and IRS-2 perform key functions in the insulin pathway. Numerous authors have suggested that single-nucleotide polymorphism (SNP) changes in the DNA sequence may be associated with the development of obesity, insulin resistance and type 2 diabetes. The Gly972Arg polymorphism of the IRS-1 gene and the Gly1057Asp polymorphism of the IRS-2 gene are believed to be associated with the occurrence of insulin resistance and obesity according to many sources. The aim of our study was to investigate the influence of these polymorphisms on the clinical parameters and to assess their correlations in obese Polish pregnant women. A total of 154 pregnant Caucasian women from the Wielkopolska region were analyzed: 78 diagnosed with overweight or obesity (study group) and 76 with normal body mass (controls). The analysis of the polymorphisms was performed using the PCR-restriction fragment length polymorphism (PCR-RFLP) method. The IRS-2 Gly1057Asp polymorphism revealed no significant correlations with excessive weight gain during pregnancy. The analysis of the IRS-1 Gly972Arg polymorphism showed an association with obesity between the study and control groups (GG-80.77%, GR-17.95%, RR-1.28% vs GG-94.74%, GR-5.26%; p = 0.023). We also observed slightly increased BMI values ​​and higher values ​​of the waist and hip circumference before pregnancy in the case of the IRS-1 Gly972Arg polymorphism. The analysis of the clinical and anthropometric parameters demonstrated no significant relationships between the genotypes of the polymorphic variants of the IRS-1 and IRS-2 genes but suggested an association between the IRS-1 Gly972Arg polymorphism and the risk for obesity.

Regulation of insulin resistance and glucose metabolism by interaction of PIM kinases and insulin receptor substrates

Insulin resistance is caused by various environmental and genetic factors leading to a number of serious health issues. Due to its multifactorial origin, molecular characterization may provide better tools for its effective treatment. On molecular level, dysregulation of signaling pathway by insulin receptor substrates (IRSs) is one of the most common reasons of this disease. IRSs are regulated by >50 serine/threonine kinases, which may have positive or negative effects on insulin sensitivity. Among these serine/threonine kinases, PIM kinases have garnered much attention as they not only affect insulin sensitivity by phosphorylating IRSs directly and/or indirectly but also alter the activities of their downstream molecules like PI3K, AKT, and mTOR. In this review, interactions of PIM kinases with IRSs and their downstream proteins and their action mechanism in the regulation of insulin resistance are elaborated. Furthermore, this review offers fundamental understandings of the role of PIM kinases in this signaling pathway.

Insulin signaling pathway and related molecules: Role in neurodegeneration and Alzheimer's disease

Alzheimer's disease (AD) is one of the most common neurodegenerative diseases. Its major pathological hallmarks, neurofibrillary tangles (NFT), and amyloid-β plaques can result from dysfunctional insulin signaling. Insulin is an important growth factor that regulates cell growth, energy utilization, mitochondrial function, autophagy, oxidative stress, synaptic plasticity, and cognitive function. Insulin and its downstream signaling molecules are located majorly in the regions of cortex and hippocampus. The major molecules involved in impaired insulin signaling include IRS, PI3K, Akt, and GSK-3β. Activation or inactivation of these major molecules through increased or decreased phosphorylation plays a role in insulin signaling abnormalities or insulin resistance. Insulin resistance, therefore, is considered as a major culprit in generating the hallmarks of AD arising from neuroinflammation and oxidative stress, etc. Moreover, caspases, Nrf2, and NF-κB influence this pathway in an indirect way. Various studies also suggest a strong link between Diabetes Mellitus and AD due to the impairment of insulin signaling pathway. Moreover, studies also depict a strong correlation of other neurodegenerative diseases such as Parkinson's disease and Huntington's disease with insulin resistance. Hence this review will provide an insight into the role of insulin signaling pathway and related molecules as therapeutic targets in AD and other neurodegenerative diseases.

PTPN11 (SHP2) Is Indispensable for Growth Factors and Cytokine Signal Transduction During Bovine Oocyte Maturation and Blastocyst Development

This study was aimed to investigate the role of SHP2 (Src-homology-2-containing phosphotyrosine phosphatase) in intricate signaling networks invoked by bovine oocyte to achieve maturation and blastocyst development. PTPN11 (Protein Tyrosine Phosphatase, non-receptor type 11) encoding protein SHP2, a positive transducer of RTKs (Receptor Tyrosine Kinases) and cytokine receptors, can play a significant role in bovine oocyte maturation and embryo development, but this phenomenon has not yet been explored. Here, we used different growth factors, cytokines, selective activator, and a specific inhibitor of SHP2 to ascertain its role in bovine oocyte developmental stages in vitro. We found that SHP2 became activated by growth factors and cytokines treatment and was highly involved in the activation of oocyte maturation and embryo development pathways. Activation of SHP2 triggered MAPK (mitogen-activated protein kinases) and PI3K/AKT (Phosphoinositide 3-kinase/Protein kinase B) signaling cascades, which is not only important for GVBD (germinal vesical breakdown) induction but also for maternal mRNA translation. Inhibition of phosphatase activity of SHP2 with PHPS1 (Phenylhydrazonopyrazolone sulfonate 1) reduced oocytes maturation as well as bovine blastocyst ICM (inner cell mass) volume. Supplementation of LIF (Leukemia Inhibitory Factor) to embryos showed an unconventional direct relation between p-SHP2 and p-STAT3 (Signal transducer and activator of transcription 3) for blastocyst ICM development. Other than growth factors and cytokines, cisplatin was used to activate SHP2. Cisplatin activated SHP2 modulate growth factors effect and combine treatment significantly enhanced quality and rate of developed blastocysts.

Sulforaphane Prevents Hepatic Insulin Resistance by Blocking Serine Palmitoyltransferase 3-Mediated Ceramide Biosynthesis

Sulforaphane (SFA), a naturally active isothiocyanate compound from cruciferous vegetables used in clinical trials for cancer treatment, was found to possess potency to alleviate insulin resistance. But its underlying molecular mechanisms are still incompletely understood. In this study, we assessed whether SFA could improve insulin sensitivity and glucose homeostasis both in vitro and in vivo by regulating ceramide production. The effects of SFA on glucose metabolism and expression levels of key proteins in the hepatic insulin signaling pathway were evaluated in insulin-resistant human hepatic carcinoma HepG2 cells. The results showed that SFA dose-dependently increased glucose uptake and intracellular glycogen content by regulating the insulin receptor substrate 1 (IRS-1)/protein kinase B (Akt) signaling pathway in insulin-resistant HepG2 cells. SFA also reduced ceramide contents and downregulated transcription of ceramide-related genes. In addition, knockdown of serine palmitoyltransferase 3 (SPTLC3) in HepG2 cells prevented ceramide accumulation and alleviated insulin resistance. Moreover, SFA treatment improved glucose tolerance and insulin sensitivity, inhibited SPTLC3 expression and hepatic ceramide production and reduced hepatic triglyceride content in vivo. We conclude that SFA recovers glucose homeostasis and improves insulin sensitivity by blocking ceramide biosynthesis through modulating SPTLC3, indicating that SFA may be a potential candidate for prevention and amelioration of hepatic insulin resistance via a ceramide-dependent mechanism.

Identification of novel mutations of Insulin Receptor Substrate 1 (IRS1) in tumor samples of non-small cell lung cancer (NSCLC): Implications for aberrant insulin signaling in development of cancer

Lung cancer is the leading cause of cancer-related death, and NSCLC constitutes nearly 85%-90% of all cases. The IRS proteins function as adaptors and transmit signals from multiple receptors. Upon binding of insulin to the insulin receptor (IR), IRS1 is phosphorylated at several YXXM motifs creating docking sites for the binding of PI3Kp85, which activates AKT kinase. Therefore, we thought that gain of function mutantions of IRS1 could be related to development of lung cancer. In line with this, we wanted determine whether the IRS1 gene was mutated in the coding regions surrounding YXXM motifs. We sequenced the coding regions surrounding YXXM motifs of IRS1 using tumor samples of 42 NSCLC patients and 40 matching controls and found heterozygote p.S668T mutation in nine of 42 samples and four of nine also had the p.D674H mutation. We generated IRS1 expression vectors harboring p.S668T, p.D674H and double mutants. Expression of the mutants differentially affected insulin-induced phosphorylation of IRS1, AKT, ERK, and STAT3. Also, our mutants induced proliferation, glucose uptake, inhibited the migration of 293T cells and affected the responsiveness of the cells to cisplatin and radiation. Our results suggest that these novel mutations play a role in the phenotype of lung cancer.

Modeling cell line-specific recruitment of signaling proteins to the insulin-like growth factor 1 receptor

Receptor tyrosine kinases (RTKs) typically contain multiple autophosphorylation sites in their cytoplasmic domains. Once activated, these autophosphorylation sites can recruit downstream signaling proteins containing Src homology 2 (SH2) and phosphotyrosine-binding (PTB) domains, which recognize phosphotyrosine-containing short linear motifs (SLiMs). These domains and SLiMs have polyspecific or promiscuous binding activities. Thus, multiple signaling proteins may compete for binding to a common SLiM and vice versa. To investigate the effects of competition on RTK signaling, we used a rule-based modeling approach to develop and analyze models for ligand-induced recruitment of SH2/PTB domain-containing proteins to autophosphorylation sites in the insulin-like growth factor 1 (IGF1) receptor (IGF1R). Models were parameterized using published datasets reporting protein copy numbers and site-specific binding affinities. Simulations were facilitated by a novel application of model restructuration, to reduce redundancy in rule-derived equations. We compare predictions obtained via numerical simulation of the model to those obtained through simple prediction methods, such as through an analytical approximation, or ranking by copy number and/or K_D value, and find that the simple methods are unable to recapitulate the predictions of numerical simulations. We created 45 cell line-specific models that demonstrate how early events in IGF1R signaling depend on the protein abundance profile of a cell. Simulations, facilitated by model restructuration, identified pairs of IGF1R binding partners that are recruited in anti-correlated and correlated fashions, despite no inclusion of cooperativity in our models. This work shows that the outcome of competition depends on the physicochemical parameters that characterize pairwise interactions, as well as network properties, including network connectivity and the relative abundances of competitors.

Cells rely on networks of interacting biomolecules to sense and respond to environmental perturbations and signals. However, it is unclear how information is processed to generate appropriate and specific responses to signals, especially given that these networks tend to share many components. For example, receptors that detect distinct ligands and regulate distinct cellular activities commonly interact with overlapping sets of downstream signaling proteins. Here, to investigate the downstream signaling of a well-studied receptor tyrosine kinase (RTK), the insulin-like growth factor 1 (IGF1) receptor (IGF1R), we formulated and analyzed 45 cell line-specific mathematical models, which account for recruitment of 18 different binding partners to six sites of receptor autophosphorylation in IGF1R. The models were parameterized using available protein copy number and site-specific affinity measurements, and restructured to allow for network generation. We find that recruitment is influenced by the protein abundance profile of a cell, with different patterns of recruitment in different cell lines. Furthermore, in a given cell line, we find that pairs of IGF1R binding partners may be recruited in a correlated or anti-correlated fashion. We demonstrate that the simulations of the model have greater predictive power than protein copy number and/or binding affinity data, and that even a simple analytical model cannot reproduce the predicted recruitment ranking obtained via simulations. These findings represent testable predictions and indicate that the outputs of IGF1R signaling depend on cell line-specific properties in addition to the properties that are intrinsic to the biomolecules involved.

Monitoring activities of receptor tyrosine kinases using a universal adapter in genetically encoded split TEV assays

Receptor tyrosine kinases (RTKs) play key roles in various aspects of cell biology, including cell-to-cell communication, proliferation and differentiation, survival, and tissue homeostasis, and have been implicated in various diseases including cancer and neurodevelopmental disorders. Ligand-activated RTKs recruit adapter proteins through a phosphotyrosine (p-Tyr) motif that is present on the RTK and a p-Tyr-binding domain, like the Src homology 2 (SH2) domain found in adapter proteins. Notably, numerous combinations of RTK/adapter combinations exist, making it challenging to compare receptor activities in standardised assays. In cell-based assays, a regulated adapter recruitment can be investigated using genetically encoded protein–protein interaction detection methods, such as the split TEV biosensor assay. Here, we applied the split TEV technique to robustly monitor the dynamic recruitment of both naturally occurring full-length adapters and artificial adapters, which are formed of clustered SH2 domains. The applicability of this approach was tested for RTKs from various subfamilies including the epidermal growth factor (ERBB) family, the insulin receptor (INSR) family, and the hepatocyte growth factor receptor (HGFR) family. Best signal-to-noise ratios of ligand-activated RTK receptor activation was obtained when clustered SH2 domains derived from GRB2 were used as adapters. The sensitivity and robustness of the RTK recruitment assays were validated in dose-dependent inhibition assays using the ERBB family-selective antagonists lapatinib and WZ4002. The RTK split TEV recruitment assays also qualify for high-throughput screening approaches, suggesting that the artificial adapter may be used as universal adapter in cell-based profiling assays within pharmacological intervention studies.

Involvement of insulin receptor substrates in cognitive impairment and Alzheimer's disease

Type 2 diabetes—associated with impaired insulin/insulin-like growth factor-1 (IGF1) signaling (IIS)—is a risk factor for cognitive impairment and dementia including Alzheimer’s disease (AD). The insulin receptor substrate (IRS) proteins are major components of IIS, which transmit upstream signals via the insulin receptor and/or IGF1 receptor to multiple intracellular signaling pathways, including AKT/protein kinase B and extracellular-signal-regulated kinase cascades. Of the four IRS proteins in mammals, IRS1 and IRS2 play key roles in regulating growth and survival, metabolism, and aging. Meanwhile, the roles of IRS1 and IRS2 in the central nervous system with respect to cognitive abilities remain to be clarified. In contrast to IRS2 in peripheral tissues, inactivation of neural IRS2 exerts beneficial effects, resulting in the reduction of amyloid β accumulation and premature mortality in AD mouse models. On the other hand, the increased phosphorylation of IRS1 at several serine sites is observed in the brains from patients with AD and animal models of AD or cognitive impairment induced by type 2 diabetes. However, these serine sites are also activated in a mouse model of type 2 diabetes, in which the diabetes drug metformin improves memory impairment. Because IRS1 and IRS2 signaling pathways are regulated through complex mechanisms including positive and negative feedback loops, whether the elevated phosphorylation of IRS1 at specific serine sites found in AD brains is a primary response to cognitive dysfunction remains unknown. Here, we examine the associations between IRS1/IRS2-mediated signaling in the central nervous system and cognitive decline.

Stable Isotope Labeling by Amino Acids in Cell Culture (SILAC) for Quantitative Proteomics

Stable isotope labeling by amino acids in cell culture (SILAC) is a powerful approach for high-throughput quantitative proteomics. SILAC allows highly accurate protein quantitation through metabolic encoding of whole cell proteomes using stable isotope labeled amino acids. Since its introduction in 2002, SILAC has become increasingly popular. In this chapter we review the methodology and application of SILAC, with an emphasis on three research areas: dynamics of posttranslational modifications, protein-protein interactions, and protein turnover.

Integrated proximal proteomics reveals IRS2 as a determinant of cell survival in ALK-driven neuroblastoma

Oncogenic anaplastic lymphoma kinase (ALK) is one of the few druggable targets in neuroblastoma, and therapy resistance to ALK-targeting tyrosine kinase inhibitors (TKIs) comprises an inevitable clinical challenge. Therefore, a better understanding of the oncogenic signaling network rewiring driven by ALK is necessary to improve and guide future therapies. Here, we performed quantitative mass spectrometry-based proteomics on neuroblastoma cells treated with one of three clinically relevant ALK TKIs (crizotinib, LDK378, or lorlatinib) or an experimentally used ALK TKI (TAE684) to unravel aberrant ALK signaling pathways. Our integrated proximal proteomics (IPP) strategy included multiple signaling layers, such as the ALK interactome, phosphotyrosine interactome, phosphoproteome, and proteome. We identified the signaling adaptor protein IRS2 (insulin receptor substrate 2) as a major ALK target and an ALK TKI-sensitive signaling node in neuroblastoma cells driven by oncogenic ALK. TKI treatment decreased the recruitment of IRS2 to ALK and reduced the tyrosine phosphorylation of IRS2. Furthermore, siRNA-mediated depletion of ALK or IRS2 decreased the phosphorylation of the survival-promoting kinase Akt and of a downstream target, the transcription factor FoxO3, and reduced the viability of three ALK-driven neuroblastoma cell lines. Collectively, our IPP analysis provides insight into the proximal architecture of oncogenic ALK signaling by revealing IRS2 as an adaptor protein that links ALK to neuroblastoma cell survival through the Akt-FoxO3 signaling axis.

Overexpression of IRS-4 Correlates with Procaspase 3 Levels in Tumoural Tissue of Patients with Colorectal Cancer

We reported that insulin receptor substrate 4 (IRS-4) levels increased in tissue from colorectal cancer (CRC) patients and promoted retinoblastoma-cyclin-dependent kinase activation. The aim of the present study was to evaluate the effect of IRS-4 on IGF-1 receptor pathway and its impact on procaspase 3 and PARP expression in RKO and HepG2 cancer cell lines. The results obtained in vitro were compared with those obtained from biopsies of patients with CRC (n = 18), tubulovillous adenomas (TA) (n = 2) and in matched adjacent normal colorectal (MANC) tissue (n = 20). IRS-4 overexpression in cultured cells induced the overactivation of IGF-1/BRK/AKT/GSK-3/β-catenin/cyclin D1 pathways, which led to increased expression of procaspase 3 and PARP protein levels. Studies carried out on CRC and TA tissues revealed the overactivation of the IGF-1 receptor signalling pathway, as well as the overexpression of procaspase 3 and PARP in tumoural tissue with respect to MANC tissue. The upregulation of IRS-4 in tumoural samples correlated significantly with the increase in pIGF-1 receptor (Tyr 1165/1166) (r = 0.84; p < 0.0001), procaspase 3 (r = 0. 77; p < 0. 0005) and PARP (r = 0. 89; p < 0. 0005). Similarly, we observed an increase in the proteolysis of procaspase 3 in tumoural tissue with respect to MANC tissue, which correlated significantly with the degradation of PARP (r = 0.86; p < 0.0001), p53 (r = 0.84; p < 0.0001), and GSK-3 (r = 0.78; p < 0.0001). The stratification of patient samples using the TNM system revealed that procaspase 3 and caspase 3 increased gradually with T values, which suggests their involvement in the size and local invasion of primary tumours. Taken together, our findings suggest that IRS-4 overexpression promotes the activation of the IGF-1 receptor pathway, which leads to the increase in procaspase 3 levels in CRC.