Linking integrin conformation to function

Characterization and functional analysis of integrin αV in Sebastes schlegelii: Implications for apoptosis, adhesion, and migration in intestinal cells

Integrins, as essential cell adhesion molecules, consist of an α subunit and a β subunit that interact with extracellular matrix proteins and cell surface ligands to mediate cellular adhesion and signaling. The integrin αV subfamily is widely expressed on the cell surface and plays a critical role in regulating cell growth, apoptosis, and various cellular processes. To explore the function of integrin αV in teleosts, we retrieved the integrin αV (SsITGαV) sequences from the Sebastes schlegelii genome and assessed the tissue expression and response to Edwardsiella tarda stimuli of SsITGαV. We evaluated the effects of SsITGαV in the intestinal cell line on apoptosis, migration, and adhesion using flow cytometry, scratch assays, and cell adhesion experiments by overexpressing and RNA interference methods. The results showed that the coding sequence of SsITGαV comprises 1055 amino acids, containing a signal peptide and a transmembrane domain. SsITGαV is expressed in various tissues, with the highest expression observed in the gill. We investigated the expression pattern of SsITGαV in the head kidney post E. tarda stimulation and observed an increase in its expression. Subcellular localization revealed that SsITGαV predominantly resides in the extracellular matrix. SsITGαV facilitated apoptosis, enhanced cell adhesion, and promoted cell migration in the intestinal cell line. According to the qRT-PCR analysis, alterations in the expression levels of apoptosis-related genes caspase-3, caspase-8, and caspase-10, along with inflammatory factors IL-1 β, IL-6, and IL-8, were positively linked to changes in SsITGαV. These findings provide insights into the function of the integrin αV gene in teleosts, establishing a foundation for further investigation into the role of the integrin α subfamily in lower vertebrates.

Multifaceted, unique role of CD11c in leukocyte biology

CD11c is widely known as a dendritic cell surface marker but its non-dendritic cell expression profiles as well as its functional role have been gradually delineated. As a member of leukocyte-specific β2 integrin family, CD11c forms a heterodimer with CD18. CD11c/CD18 takes different conformations, which dictate its ligand binding. Here we reviewed CD11c current state of art, in comparison to its sister proteins CD11a, CD11b, and CD11d, illustrating its unique feature in leukocyte biology.

Switching Roles─Exploring Concentration-Dependent Agonistic versus Antagonistic Behavior of Integrin Ligands

Identification of integrins as cancer targets has stimulated the development of specific inhibitory ligands. However, following cilengitide's unexpected clinical failure by promoting angiogenesis at low concentrations, pure ligand antagonism was soon scrutinized. We evaluated αvβ3, αvβ6, or α5β1 ligands for concentration-dependent functional switches in respective integrin subtype-overexpressing cancer cells. Cilengitide (L2) or L1 provoked minor transient changes in (p)-FAK and (p)-p44/42(erk-1/2) predominantly at low concentrations and antagonized cell migration at high concentrations, while agonistically accelerating it at low concentrations. L5 (α5β1) showed bell-shaped FAK activation at both concentrations, blocking cell migration at high concentrations only in α5β1+ OV-MZ-6 cells, not acting agonistically. L3 (αvβ6) did not alter signaling upon long exposure but transiently and early activated FAK in αvβ6+ HN cells at both concentrations, with neither antagonistic nor agonistic consequences on cell motility. These data underscore the need for in-depth evaluation of ligand actions to ensure their most promising medical use.

Integrins in Cardiovascular Health and Disease: Molecular Mechanisms and Therapeutic Opportunities

Cardiovascular diseases, including atherosclerosis, hypertension, and heart failure, remain the leading cause of global mortality, with endothelial dysfunction and vascular remodeling as critical contributors. Integrins, as transmembrane adhesion proteins, are central regulators of cell adhesion, migration, and signaling, playing a pivotal role in maintaining vascular homeostasis and mediating pathological processes such as inflammation, angiogenesis, and extracellular matrix remodeling. This article comprehensively examines the role of integrins in the pathogenesis of cardiovascular diseases, focusing on their dysfunction in endothelial cells and interactions with inflammatory mediators, such as TNF-α. Molecular mechanisms of integrin action are discussed, including their involvement in mechanotransduction, leukocyte adhesion, and signaling pathways that regulate vascular integrity. The review also highlights experimental findings, such as the use of specific integrin-targeting plasmids and immunofluorescence to elucidate integrin functions under inflammatory conditions. Additionally, potential therapeutic strategies are explored, including the development of integrin inhibitors, monoclonal antibodies, and their application in regenerative medicine. These approaches aim not only to mitigate pathological vascular remodeling but also to promote tissue repair and angiogenesis. By bridging insights from molecular studies with their translational potential, this work underscores the promise of integrin-based therapies in advancing the management and treatment of cardiovascular diseases.

Conformational response of αIIbβ3 and αVβ3 integrins to force

As major adhesion receptors, integrins transmit biochemical and mechanical signals across the plasma membrane. These functions are regulated by transitions between bent and extended conformations and modulated by force. To understand how force on integrins mediates cellular mechanosensing, we compared two highly homologous integrins, αIIbβ3 and αVβ3. These integrins, expressed in circulating platelets vs. solid tissues, respectively, share the β3 subunit, bind similar ligands and have similar bent and extended conformations. Here, we report that in cells expressing equivalent levels of each integrin, αIIbβ3 mediates spreading on softer substrates than αVβ3. These effects correlate with differences in structural dynamics of the two integrins under force. All-atom simulations show that αIIbβ3 is more flexible than αVβ3 due to correlated residue motions within the α subunit domains. Single molecule measurements confirm that αIIbβ3 extends faster than αVβ3. These results reveal a fundamental relationship between protein function and structural dynamics in cell mechanosensing.

Small molecule- and peptide-drug conjugates addressing integrins: A story of targeted cancer treatment

Targeted cancer treatment should avoid side effects and damage to healthy cells commonly encountered during traditional chemotherapy. By combining small molecule or peptidic ligands as homing devices with cytotoxic drugs connected by a cleavable or non-cleavable linker in peptide-drug conjugates (PDCs) or small molecule-drug conjugates (SMDCs), cancer cells and tumours can be selectively targeted. The development of highly affine, selective peptides and small molecules in recent years has allowed PDCs and SMDCs to increasingly compete with antibody-drug conjugates (ADCs). Integrins represent an excellent target for conjugates because they are overexpressed by most cancer cells and because of the broad knowledge about native binding partners as well as the multitude of small-molecule and peptidic ligands that have been developed over the last 30 years. In particular, integrin αVβ3 has been addressed using a variety of different PDCs and SMDCs over the last two decades, following various strategies. This review summarises and describes integrin-addressing PDCs and SMDCs while highlighting points of great interest.

Exercise-inducible circulating extracellular vesicle irisin promotes browning and the thermogenic program in white adipose tissue

AIM

Exercise can reduce body weight and promote white fat browning, but the underlying mechanisms remain largely unknown. This study investigated the role of fibronectin type III domain-containing protein 5 (FNDC5)/Irisin, a hormone released from exercising muscle, in the browning of white fat in circulating extracellular vesicles (EVs).

METHODS

Mice were subjected to a 4 weeks of running table exercise, and fat browning was analyzed via histology, protein blotting and qPCR. Circulating EVs were extracted by ultrahigh-speed centrifugation, and ELISA was used to measure the irisin concentration in the circulating EVs. Circulating EVs that differentially expressed irisin were applied to adipocytes, and the effect of EV-irisin on adipocyte energy metabolism was analyzed by immunofluorescence, protein blotting, and cellular oxygen consumption rate analysis.

RESULTS

During sustained exercise, the mice lost weight and developed fat browning. FNDC5 was induced, cleaved, and secreted into irisin, and irisin levels subsequently increased in the plasma during exercise. Interestingly, irisin was highly expressed in circulating EVs that effectively promoted adipose browning. Mechanistically, the circulating EV-irisin complex is transported intracellularly by the adipocyte membrane receptor integrin αV, which in turn activates the AMPK signaling pathway, which is dependent on mitochondrial uncoupling protein 1 to cause mitochondrial plasmonic leakage and promote heat production. After inhibition of the AMPK signaling pathway, the effects of the EV-irisin on promoting fat browning were minimal.

CONCLUSION

Exercise leads to the accumulation of circulating EV-irisin, which enhances adipose energy metabolism and thermogenesis and promotes white fat browning in mice, leading to weight loss.

Toward the mechanism of jarastatin (rJast) inhibition of the integrin αVβ3

Disintegrins are a family of cysteine-rich small proteins that were first identified in snake venom. The high divergence of disintegrins gave rise to a plethora of functions, all related to the interaction with integrins. Disintegrins evolved to interact selectively with different integrins, eliciting many physiological outcomes and being promising candidates for the therapy of many pathologies. We used NMR to determine the structure and dynamics of the recombinant disintegrin jarastatin (rJast) and its interaction with the cancer-related integrin αVβ3. rJast displayed the canonical fold of a medium-sized disintegrin and showed complex dynamic in multiple timescales. We used NMR experiments to map the interaction of rJast with αVβ3, and molecular docking followed by molecular dynamics (MD) simulation to describe the first structural model of a disintegrin/integrin complex. We showed that not only the RGD loop participates in the interaction, but also the N-terminal domain. rJast plasticity was essential for the interaction with αVβ3 and correlated with the main modes of motion depicted in the MD trajectories. In summary, our study provides novel structural insights that enhance our comprehension of the mechanisms underlying disintegrin functionality.

Thy-1 (CD90)-regulated cell adhesion and migration of mesenchymal cells: insights into adhesomes, mechanical forces, and signaling pathways

Cell adhesion and migration depend on the assembly and disassembly of adhesive structures known as focal adhesions. Cells adhere to the extracellular matrix (ECM) and form these structures via receptors, such as integrins and syndecans, which initiate signal transduction pathways that bridge the ECM to the cytoskeleton, thus governing adhesion and migration processes. Integrins bind to the ECM and soluble or cell surface ligands to form integrin adhesion complexes (IAC), whose composition depends on the cellular context and cell type. Proteomic analyses of these IACs led to the curation of the term adhesome, which is a complex molecular network containing hundreds of proteins involved in signaling, adhesion, and cell movement. One of the hallmarks of these IACs is to sense mechanical cues that arise due to ECM rigidity, as well as the tension exerted by cell-cell interactions, and transduce this force by modifying the actin cytoskeleton to regulate cell migration. Among the integrin/syndecan cell surface ligands, we have described Thy-1 (CD90), a GPI-anchored protein that possesses binding domains for each of these receptors and, upon engaging them, stimulates cell adhesion and migration. In this review, we examine what is currently known about adhesomes, revise how mechanical forces have changed our view on the regulation of cell migration, and, in this context, discuss how we have contributed to the understanding of signaling mechanisms that control cell adhesion and migration.

Mending a broken heart by biomimetic 3D printed natural biomaterial-based cardiac patches: a review

Myocardial infarction is one of the major causes of mortality as well as morbidity around the world. Currently available treatment options face a number of drawbacks, hence cardiac tissue engineering, which aims to bioengineer functional cardiac tissue, for application in tissue repair, patient specific drug screening and disease modeling, is being explored as a viable alternative. To achieve this, an appropriate combination of cells, biomimetic scaffolds mimicking the structure and function of the native tissue, and signals, is necessary. Among scaffold fabrication techniques, three-dimensional printing, which is an additive manufacturing technique that enables to translate computer-aided designs into 3D objects, has emerged as a promising technique to develop cardiac patches with a highly defined architecture. As a further step toward the replication of complex tissues, such as cardiac tissue, more recently 3D bioprinting has emerged as a cutting-edge technology to print not only biomaterials, but also multiple cell types simultaneously. In terms of bioinks, biomaterials isolated from natural sources are advantageous, as they can provide exceptional biocompatibility and bioactivity, thus promoting desired cell responses. An ideal biomimetic cardiac patch should incorporate additional functional properties, which can be achieved by means of appropriate functionalization strategies. These are essential to replicate the native tissue, such as the release of biochemical signals, immunomodulatory properties, conductivity, enhanced vascularization and shape memory effects. The aim of the review is to present an overview of the current state of the art regarding the development of biomimetic 3D printed natural biomaterial-based cardiac patches, describing the 3D printing fabrication methods, the natural-biomaterial based bioinks, the functionalization strategies, as well as the in vitro and in vivo applications.

Molecular Modeling Insights into the Structure and Behavior of Integrins: A Review

Integrins are heterodimeric glycoproteins crucial to the physiology and pathology of many biological functions. As adhesion molecules, they mediate immune cell trafficking, migration, and immunological synapse formation during inflammation and cancer. The recognition of the vital roles of integrins in various diseases revealed their therapeutic potential. Despite the great effort in the last thirty years, up to now, only seven integrin-based drugs have entered the market. Recent progress in deciphering integrin functions, signaling, and interactions with ligands, along with advancement in rational drug design strategies, provide an opportunity to exploit their therapeutic potential and discover novel agents. This review will discuss the molecular modeling methods used in determining integrins' dynamic properties and in providing information toward understanding their properties and function at the atomic level. Then, we will survey the relevant contributions and the current understanding of integrin structure, activation, the binding of essential ligands, and the role of molecular modeling methods in the rational design of antagonists. We will emphasize the role played by molecular modeling methods in progress in these areas and the designing of integrin antagonists.

Regulation of Kinase Signaling Pathways by α6β4-Integrins and Plectin in Prostate Cancer

Hemidesmosomes (HDs) are adhesive structures that ensure stable anchorage of cells to the basement membrane. They are formed by α6β4-integrin heterodimers and linked to intermediate filaments via plectin. It has been reported that one of the most common events during the pathogenesis of prostate cancer (PCa) is the loss of HD organization. While the expression levels of β4-integrins are strongly reduced, the expression levels of α6-integrins and plectin are maintained or even elevated, and seem to promote tumorigenic properties of PCa cells, such as proliferation, invasion, metastasis, apoptosis- and drug-resistance. In this review, we discuss the potential mechanisms of how HD components might contribute to various cellular signaling pathways to promote prostate carcinogenesis. Moreover, we summarize the current knowledge on the involvement of α6β4-integrins and plectin in PCa initiation and progression.

Cancer metastasis chemoprevention prevents circulating tumour cells from germination

The war against cancer traces back to the signature event half-a-century ago when the US National Cancer Act was signed into law. The cancer crusade costs trillions with disappointing returns, teasing the possibility of a new breakthrough. Cure for cancer post-metastases still seems tantalisingly out of reach. Once metastasized, cancer-related death is extremely difficult, if not impossible, to be reversed. Here we present cancer pre-metastasis chemoprevention strategy that can prevent circulating tumour cells (CTCs) from initiating metastases safely and effectively, and is disparate from the traditional cancer chemotherapy and cancer chemoprevention. Deep learning of the biology of CTCs and their disseminating organotropism, complexity of their adhesion to endothelial niche reveals that if the adhesion of CTCs to their metastasis niche (the first and the most important part in cancer metastatic cascade) can be pharmaceutically interrupted, the lethal metastatic cascade could be prevented from getting initiated. We analyse the key inflammatory and adhesive factors contributing to CTC adhesion/germination, provide pharmacological fundamentals for abortifacients to intervene CTC adhesion to the distant metastasis sites. The adhesion/inhibition ratio (AIR) is defined for selecting the best cancer metastasis chemopreventive candidates. The successful development of such new therapeutic modalities for cancer metastasis chemoprevention has great potential to revolutionise the current ineffective post-metastasis treatments.

Cryo-electron Microscopic Analysis of Single-Pass Transmembrane Receptors

Single-pass transmembrane receptors (SPTMRs) represent a diverse group of integral membrane proteins that are involved in many essential cellular processes, including signal transduction, cell adhesion, and transmembrane transport of materials. Dysregulation of the SPTMRs is linked with many human diseases. Despite extensive efforts in past decades, the mechanisms of action of the SPTMRs remain incompletely understood. One major hurdle is the lack of structures of the full-length SPTMRs in different functional states. Such structural information is difficult to obtain by traditional structural biology methods such as X-ray crystallography and nuclear magnetic resonance (NMR). The recent rapid development of single-particle cryo-electron microscopy (cryo-EM) has led to an exponential surge in the number of high-resolution structures of integral membrane proteins, including SPTMRs. Cryo-EM structures of SPTMRs solved in the past few years have tremendously improved our understanding of how SPTMRs function. In this review, we will highlight these progresses in the structural studies of SPTMRs by single-particle cryo-EM, analyze important structural details of each protein involved, and discuss their implications on the underlying mechanisms. Finally, we also briefly discuss remaining challenges and exciting opportunities in the field.

Mechanical regulation of signal transduction in angiogenesis

Biophysical and biochemical cues work in concert to regulate angiogenesis. These cues guide angiogenesis during development and wound healing. Abnormal cues contribute to pathological angiogenesis during tumor progression. In this review, we summarize the known signaling pathways involved in mechanotransduction important to angiogenesis. We discuss how variation in the mechanical microenvironment, in terms of stiffness, ligand availability, and topography, can modulate the angiogenesis process. We also present an integrated view on how mechanical perturbations, such as stretching and fluid shearing, alter angiogenesis-related signal transduction acutely, leading to downstream gene expression. Tissue engineering-based approaches to study angiogenesis are reviewed too. Future directions to aid the efforts in unveiling the comprehensive picture of angiogenesis are proposed.

Follow that cell: leukocyte migration in L-plastin mutant zebrafish

Actin assemblies are important in motile cells such as leukocytes which form dynamic plasma membrane extensions or podia. L-plastin (LCP1) is a leukocyte-specific calcium-dependent actin-bundling protein that, in mammals, is known to affect immune cell migration. Previously, we generated CRISPR/Cas9 engineered zebrafish lacking L-plastin (lcp1-/-) and reported that they had reduced survival to adulthood, suggesting that lack of this actin-bundler might negatively affect the immune system. To test this hypothesis, we examined the distribution and migration of neutrophils and macrophages in the transparent tail of early zebrafish larvae using cell-specific markers and an established wound-migration assay. Knockout larvae were similar to their heterozygous siblings in having equal body sizes and comparable numbers of neutrophils in caudal hematopoietic tissue at two days post-fertilization, indicating no gross defect in neutrophil production or developmental migration. When stimulated by a tail wound, all genotypes of neutrophils were equally migratory in a two-hour window. However for macrophages we observed both migration defects and morphological differences. L-plastin knockout macrophages (lcp1 -/-) still homed to wounds but were slower, less directional and had a star-like morphology with many leading and trailing projections. In contrast, heterozygous macrophages lcp1 (+/-) were faster, more directional, and had a streamlined, slug-like morphology. Overall, these findings show that in larval zebrafish L-plastin knockout primarily affects the macrophage response with possible consequences for organismal immunity. Consistent with our observations, we propose a model in which cytoplasmic L-plastin negatively regulates macrophage integrin adhesion by holding these transmembrane heterodimers in a 'clasped', inactive form and is a necessary part of establishing macrophage polarity during chemokine-induced motility. This article is protected by copyright. All rights reserved.

Solubilization and Purification of α5β1 Integrin from Rat Liver for Reconstitution into Nanodiscs

Transmembrane proteins (or integral membrane proteins) are synthesized in the endoplasmic reticulum where most of them are core glycosylated prior to folding and in some cases assembly into quaternary structures. Correctly glycosylated, folded, and assembled transmembrane proteins are then shuttled to the Golgi apparatus for additional posttranslational modifications such as complex-type glycosylations, sulfation or proteolytic clipping. At the plasma membrane, the glycosylated extracellular domains are key to communicate with the cellular environment for a variety of functions, such as binding to the extracellular matrix for cell adhesion and migration, to neighboring cells for cell-cell interaction, or to extracellular components for nutrient uptake and cell signaling. Intracellular domains are essential to mediate signaling cascades, or to connect to cytosolic adaptors for internalization and intracellular compartmentalization. Despite its importance for the understanding of molecular mechanisms of transmembrane protein function, the determination of their structures has remained a challenging task. In recent years, their reconstitution in lipid nanodiscs in combination with high resolution cryo-electron microscopy has provided novel avenues to render this process more accessible. Here, we describe detailed protocols for the solubilization of heavily glycosylated α₅β₁ integrin from rat livers, its purification and reconstitution into nanodiscs. At the plasma membrane of many cells, including tumor metastases, this essential heterodimeric transmembrane protein mediates the communication between extracellular matrix and cytosolic cytoskeleton in processes of cell adhesion and migration. We expect that the protocols that are described here will provide new opportunities for the determination of the full structure of α₅β₁ integrin, as well as for the understanding of how interacting partners can regulate function and activity of this transmembrane protein.

Pathways of integrins in the endo-lysosomal system

In this review, we present recent scientific advances about integrin trafficking in the endo-lysosomal system. In the last few years, plenty of new information has emerged about the endo-lysosomal system, integrins, and the mechanism, how exactly the intracellular trafficking of integrins is regulated. We review the internalization and recycling pathways of integrins, and we provide information about the possible ways of lysosomal degradation through the endosomal and autophagic system. The regulation of integrin internalization and recycling proved to be a complex process worth studying. Trafficking of integrins, together with the regulation of their gene expression, defines cellular adhesion and cellular migration through bidirectional signalization and ligand binding. Thus, any malfunction in this system can potentially (but not necessarily) lead to tumorigenesis or metastasis. Hence, extensive examinations of integrins in the endo-lysosomal system raise the possibility to identify potential new medical targets. Furthermore, this knowledge can also serve as a basis for further determination of integrin signaling- and adhesion-related processes.

Integrin Crosstalk and Its Effect on the Biological Functions of the Trabecular Meshwork/Schlemm’s Canal

Integrins are a family of heterodimeric receptors composed of an α- and β-subunit that mediate cell-adhesion to a number of extracellular matrix (ECM) proteins in the Trabecular Meshwork/Schlemm’s canal (TM/SC) of the eye. Upon binding an ECM ligand, integrins transmit signals that activate a number of signaling pathways responsible for regulating actin-mediated processes (i.e phagocytosis, cell contractility, and fibronectin fibrillogenesis) that play an important role in regulating intraocular pressure (IOP) and may be involved in glaucoma. An important function of integrin-mediated signaling events is that the activity of one integrin can affect the activity of other integrins in the same cell. This creates a crosstalk that allows TM/SC cells to respond to changes in the ECM presumably induced by the mechanical forces on the TM/SC, aging and disease. In this review, we discuss how integrin crosstalk influences the function of the human TM/SC pathway. In particular, we will discuss how different crosstalk pathways mediated by either the αvβ3 or α4β1 integrins can play opposing roles in the TM when active and therefore act as on/off switches to modulate the cytoskeleton-mediated processes that regulate the outflow of aqueous humor through the TM/SC.

Functions and clinical significance of mechanical tumor microenvironment: cancer cell sensing, mechanobiology and metastasis

Dynamic and heterogeneous interaction between tumor cells and the surrounding microenvironment fuels the occurrence, progression, invasion, and metastasis of solid tumors. In this process, the tumor microenvironment (TME) fractures cellular and matrix architecture normality through biochemical and mechanical means, abetting tumorigenesis and treatment resistance. Tumor cells sense and respond to the strength, direction, and duration of mechanical cues in the TME by various mechanotransduction pathways. However, far less understood is the comprehensive perspective of the functions and mechanisms of mechanotransduction. Due to the great therapeutic difficulties brought by the mechanical changes in the TME, emerging studies have focused on targeting the adverse mechanical factors in the TME to attenuate disease rather than conventionally targeting tumor cells themselves, which has been proven to be a potential therapeutic approach. In this review, we discussed the origins and roles of mechanical factors in the TME, cell sensing, mechano‐biological coupling and signal transduction, in vitro construction of the tumor mechanical microenvironment, applications and clinical significance in the TME.

β2-Integrins - Regulatory and Executive Bridges in the Signaling Network Controlling Leukocyte Trafficking and Migration

Leukocyte trafficking is an essential process of immunity, occurring as leukocytes travel within the bloodstream and as leukocyte migration within tissues. While it is now established that leukocytes can utilize the mesenchymal migration mode or amoeboid migration mode, differences in the migratory behavior of leukocyte subclasses and how these are realized on a molecular level in each subclass is not fully understood. To outline these differences, first migration modes and their dependence on parameters of the extracellular environments will be explained, as well as the intracellular molecular machinery that powers migration in general. Extracellular parameters are detected by adhesion receptors such as integrins. β2-integrins are surface receptors exclusively expressed on leukocytes and are essential for leukocytes exiting the bloodstream, as well as in mesenchymal migration modes, however, integrins are dispensable for the amoeboid migration mode. Additionally, the balance of different RhoGTPases - which are downstream of surface receptor signaling, including integrins - mediate formation of membrane structures as well as actin dynamics. Individual leukocyte subpopulations have been shown to express distinct RhoGTPase profiles along with their differences in migration behavior, which will be outlined. Emerging aspects of leukocyte migration include signal transduction from integrins via actin to the nucleus that regulates DNA status, gene expression profiles and ultimately leukocyte migratory phenotypes, as well as altered leukocyte migration in tumors, which will be touched upon.

Aptamer Targets Triple-Negative Breast Cancer through Specific Binding to Surface CD49c

Simple Summary

Targeted therapy directed against many biomarkers has not shown significant improvement in outcome in TNBC, and therefore it is urgent to discover more biomarker candidates. Here, we found a DNA aptamer that bound to TNBC cells and identified CD49c as a specific surface marker for TNBC cells using the aptamer-facilitated biomarker discovery technology. The findings suggest that this DNA aptamer can be a drug delivery vehicle and CD49c is a potential target of targeted therapy for TNBC.

Abstract

Although targeted cancer therapy can induce higher therapeutic efficacy and cause fewer side effects in patients, the lack of targetable biomarkers on triple-negative breast cancer (TNBC) cells limits the development of targeted therapies by antibody technology. Therefore, we investigated an alternative approach to target TNBC by using the PDGC21T aptamer, which selectively binds to poorly differentiated carcinoma cells and tumor tissues, although the cellular target is still unknown. We found that synthetic aptamer probes specifically bound cultured TNBC cells in vitro and selectively targeted TNBC xenografts in vivo. Subsequently, to identify the target molecule on TNBC cells, we performed aptamer-mediated immunoprecipitation in lysed cell membranes followed by liquid chromatography tandem mass spectrometry (LC-MS/MS). Sequencing analysis revealed a highly conserved peptide sequence consistent with the cell surface protein CD49c (integrin α3). For target validation, we stained cultured TNBC and non-TNBC cells with an aptamer probe or a CD49c antibody and found similar cell staining patterns. Finally, competition cell-binding assays using both aptamer and anti-CD49c antibody revealed that CD49c is the biomarker targeted by the PDGC21T aptamer on TNBC cells. Our findings provide a molecular foundation for the development of targeted TNBC therapy using the PDGC21T aptamer as a targeting ligand.

Magnetogenetics: remote activation of cellular functions triggered by magnetic switches

During the last decade, the possibility to remotely control intracellular pathways using physical tools has opened the way to novel and exciting applications, both in basic research and clinical applications. Indeed, the use of physical and non-invasive stimuli such as light, electricity or magnetic fields offers the possibility of manipulating biological processes with spatial and temporal resolution in a remote fashion. The use of magnetic fields is especially appealing for in vivo applications because they can penetrate deep into tissues, as opposed to light. In combination with magnetic actuators they are emerging as a new instrument to precisely manipulate biological functions. This approach, coined as magnetogenetics, provides an exclusive tool to study how cells transform mechanical stimuli into biochemical signalling and offers the possibility of activating intracellular pathways connected to temperature-sensitive proteins. In this review we provide a critical overview of the recent developments in the field of magnetogenetics. We discuss general topics regarding the three main components for magnetic field-based actuation: the magnetic fields, the magnetic actuators and the cellular targets. We first introduce the main approaches in which the magnetic field can be used to manipulate the magnetic actuators, together with the most commonly used magnetic field configurations and the physicochemical parameters that can critically influence the magnetic properties of the actuators. Thereafter, we discuss relevant examples of magneto-mechanical and magneto-thermal stimulation, used to control stem cell fate, to activate neuronal functions, or to stimulate apoptotic pathways, among others. Finally, although magnetogenetics has raised high expectations from the research community, to date there are still many obstacles to be overcome in order for it to become a real alternative to optogenetics for instance. We discuss some controversial aspects related to the insufficient elucidation of the mechanisms of action of some magnetogenetics constructs and approaches, providing our opinion on important challenges in the field and possible directions for the upcoming years.

Recent Progress of RGD Modified Liposomes as Multistage Rocket Against Cancer

Cancer is a life-threatening disease, contributing approximately 9.4 million deaths worldwide. To address this challenge, scientific researchers have investigated molecules that could act as speed-breakers for cancer. As an abiotic drug delivery system, liposomes can hold both hydrophilic and lipophilic drugs, which promote a controlled release, accumulate in the tumor microenvironment, and achieve elongated half-life with an enhanced safety profile. To further improve the safety and impair the off-target effect, the surface of liposomes could be modified in a way that is easily identified by cancer cells, promotes uptake, and facilitates angiogenesis. Integrins are overexpressed on cancer cells, which upon activation promote downstream cell signaling and eventually activate specific pathways, promoting cell growth, proliferation, and migration. RGD peptides are easily recognized by integrin over expressed cells. Just like a multistage rocket, ligand anchored liposomes can be selectively recognized by target cells, accumulate at the specific site, and finally, release the drug in a specific and desired way. This review highlights the role of integrin in cancer development, so gain more insights into the phenomenon of tumor initiation and survival. Since RGD is recognized by the integrin family, the fate of RGD has been demonstrated after its binding with the acceptor’s family. The role of RGD based liposomes in targeting various cancer cells is also highlighted in the paper.

Molecular dynamics simulations, docking and MMGBSA studies of newly designed peptide-conjugated glucosyloxy stilbene derivatives with tumor cell receptors

In this work, for the first time, we designed derivatives of beta-D-glucosyloxy-3-hydroxy-trans-stiblene-2-carboxylic acid (GHS), by conjugating GHS with tumor targeting peptides RPARPAR and GGKRPAR to target over-expressed receptors in tumor cells. The sequences RPARPAR and GGKRPAR are known to target the neuropilin1 (NRP1) receptor due to the C-terminal Arg domain; however, their effectiveness has never been examined with other commonly over-expressed receptors in tumor cells, particularly of chronic lymphocytic leukemia that include integrin α1β1 and CD22. By conjugating these peptides with GHS, which is known for its inherent anti-cancer properties, the goal is to further enhance tumor cell targeting by developing compounds that can target multiple receptors. The physicochemical properties of the conjugates and individual peptides were analyzed using Turbomole and COSMOthermX20 in order to determine their hydrogen bond accepting and donating capabilities. The web server POCASA was used in order to determine the surface cavities and binding pockets of the three receptors. To explore the binding affinities, we conducted molecular docking studies with the peptides and the conjugates with each of the receptors. After molecular docking, the complexes were analyzed using Protein-Ligand Interaction Profiler to determine the types of interactions involved. Molecular dynamics simulation studies were conducted to explore the stability of the receptor-ligand complexes. Our results indicated that in most cases the conjugates showed higher binding and stability with the receptors. Additionally, highly stable complexes of conjugates were obtained with CD22, NRP1 and in most cases with the integrin α1β1 receptor as well. The binding energies were calculated for each of the receptor ligand complexes through trajectory analysis using MMGBSA studies. SwissADME studies revealed that the compounds showed low GI absorption and were not found to be CYP inhibitors and had bioavailability score that would allow them to be considered as potential drug candidates. Overall, our results for the first time show that the designed conjugates can target multiple over-expressed receptors in tumor cells and may be potentially developed as future therapeutics for targeting tumor cells.

β2 Integrin CD11d/CD18: From Expression to an Emerging Role in Staged Leukocyte Migration

CD11d/CD18 is the most recently discovered and least understood β2 integrin. Known CD11d adhesive mechanisms contribute to both extravasation and mesenchymal migration – two key aspects for localizing peripheral leukocytes to sites of inflammation. Differential expression of CD11d induces differences in monocyte/macrophage mesenchymal migration including impacts on macrophage sub-set migration. The participation of CD11d/CD18 in leukocyte localization during atherosclerosis and following neurotrauma has sparked interest in the development of CD11d-targeted therapeutic agents. Whereas the adhesive properties of CD11d have undergone investigation, the signalling pathways induced by ligand binding remain largely undefined. Underlining each adhesive and signalling function, CD11d is under unique transcriptional control and expressed on a sub-set of predominately tissue-differentiated innate leukocytes. The following review is the first to capture the nearly three decades of CD11d research and discusses the emerging role of CD11d in leukocyte migration and retention during the progression of a staged immune response.

ANGPTL2 Promotes Inflammation via Integrin α5β1 in Chondrocytes

BACKGROUND

Angiopoietin-like protein 2 (ANGPTL2) is a secreted molecule with numerous physiologic and pathologic functions, for example, in angiogenesis, hematopoiesis, and tumorigenesis. Although recent studies implicated ANGPTL2 in chronic inflammation in mouse peritoneal macrophages, human ligamentum flavum fibroblasts, and human retinal microvascular endothelial cells, the mechanism underlying ANGPTL2-associated inflammation in chondrocytes remains unclear. Therefore, it was investigated whether ANGPTL2 is expressed in or functions in chondrocytes.

METHODS

Expression of ANGPTL2 and its receptor, integrin α5β1 were examined over time in ATDC5 cells using real-time RT-PCR (reverse transcription-polymerase chain reaction) analysis. ATDC5 cells were then incubated with or without ANGPTL2 for 3 hours, and expression of the IL-1β, TNF-α, COX-2, aggrecanase (ADAMTS)-5, matrix metalloproteinase (MMP)-3, and MMP-13 genes were examined using real-time RT-PCR. Additionally, phosphorylation of ERK, JNK, p38, Akt, and NF-κB was examined by western blotting. Furthermore, it was also investigated for the effect of anti-integrin α₅β₁ antibody on the expression of inflammatory markers and intracellular signaling pathways.

RESULTS

ANGPTL2 induced the phosphorylation of all 3 MAPKs, Akt, and NF-κB and dramatically upregulated the expression of inflammation-related factor genes. Inhibiting the activation of integrin α5β1 suppressed these reactions.

CONCLUSION

ANGPTL2 may induce inflammatory factors by stimulating the integrin α5β1/MAPKs, Akt, and NF-κB signaling pathway.

Identification of Oleanolic Acid as Allosteric Agonist of Integrin αM by Combination of In Silico Modeling and In Vitro Analysis

Oleanolic acid is a widely distributed natural product, which possesses promising antitumor, antiviral, antihyperlipidemic, and anti-inflammatory activities. A heterodimeric complex formed by integrin α_M (CD11b) and integrin β₂ (CD18) is highly expressed on monocytes and macrophages. In the current study, we demonstrate that the I domain of α_M (α_M-I domain) might present a potential cellular target for oleanolic acid. In vitro data show that oleanolic acid induces clustering of α_M on macrophages and reduces their non-directional migration. In accordance with experimental data, molecular docking revealed that oleanolic acid binds to the α_M-I domain in its extended-open form, the dominant conformation found in α_M clusters. Molecular dynamics simulation revealed that oleanolic acid can increase the flexibility of the α7 helix and promote its movement away from the N-terminus, indicating that oleanolic acid may facilitate the conversion of the α_M-I domain from the extended-closed to the extended-open conformation. As demonstrated by metadynamics simulation, oleanolic acid can destabilize the local minimum of the α_M-I domain in the open conformation partially through disturbance of the interactions between α1 and α7 helices. In summary, we demonstrate that oleanolic acid might function as an allosteric agonist inducing clustering of α_M on macrophages by shifting the balance from the closed to the extended-open conformation. The molecular target identified in this study might hold potential for a purposeful use of oleanolic acid to modulate chronic inflammatory responses.

EphA2 signaling within integrin adhesions regulates fibrillar adhesion elongation and fibronectin deposition

The multifunctional glycoprotein fibronectin influences several crucial cellular processes and contributes to multiple pathologies. While a link exists between fibronectin-associated pathologies and the receptor tyrosine kinase EphA2, the mechanism by which EphA2 promotes fibronectin matrix remodeling remains unknown. We previously demonstrated that EphA2 deletion reduces smooth muscle fibronectin deposition and blunts fibronectin deposition in atherosclerosis without influencing fibronectin expression. We now show that EphA2 expression is required for contractility-dependent elongation of tensin- and α5β1 integrin-rich fibrillar adhesions that drive fibronectin fibrillogenesis. Mechanistically, EphA2 localizes to integrin adhesions where focal adhesion kinase mediates ligand-independent Y772 phosphorylation, and mutation of this site significantly blunts fibrillar adhesion length. EphA2 deficiency decreases smooth muscle cell contractility by enhancing p190RhoGAP activation and reducing RhoA activity, whereas stimulating RhoA signaling in EphA2 deficient cells rescues fibrillar adhesion elongation. Together, these data identify EphA2 as a novel regulator of fibrillar adhesion elongation and provide the first data identifying a role for EphA2 signaling in integrin adhesions.

Myosin-X and talin modulate integrin activity at filopodia tips

Filopodia assemble unique integrin-adhesion complexes to sense the extracellular matrix. However, the mechanisms of integrin regulation in filopodia are poorly defined. Here, we report that active integrins accumulate at the tip of myosin-X (MYO10)-positive filopodia, while inactive integrins are uniformly distributed. We identify talin and MYO10 as the principal integrin activators in filopodia. In addition, deletion of MYO10's FERM domain, or mutation of its β1-integrin-binding residues, reveals MYO10 as facilitating integrin activation, but not transport, in filopodia. However, MYO10's isolated FERM domain alone cannot activate integrins, potentially because of binding to both integrin tails. Finally, because a chimera construct generated by swapping MYO10-FERM by talin-FERM enables integrin activation in filopodia, our data indicate that an integrin-binding FERM domain coupled to a myosin motor is a core requirement for integrin activation in filopodia. Therefore, we propose a two-step integrin activation model in filopodia: receptor tethering by MYO10 followed by talin-mediated integrin activation.

Integrins as attractive targets for cancer therapeutics

Integrins are transmembrane receptors that have been implicated in the biology of various human physiological and pathological processes. These molecules facilitate cell–extracellular matrix and cell–cell interactions, and they have been implicated in fibrosis, inflammation, thrombosis, and tumor metastasis. The role of integrins in tumor progression makes them promising targets for cancer treatment, and certain integrin antagonists, such as antibodies and synthetic peptides, have been effectively utilized in the clinic for cancer therapy. Here, we discuss the evidence and knowledge on the contribution of integrins to cancer biology. Furthermore, we summarize the clinical attempts targeting this family in anti-cancer therapy development.

Growth factors produced by bone marrow stromal cells on nanoroughened titanium-aluminum-vanadium surfaces program distal MSCs into osteoblasts via BMP2 signaling

Statement of Clinical Significance: There remains the need to develop materials and surfaces that can increase the rate of implant osseointegration. Though osteoanabolic agents, like bone morphogenetic protein (BMP), can provide signaling for osteogenesis, the appropriate design of implants can also produce an innate cellular response that may reduce or eliminate the need to use additional agents to stimulate bone formation. Studies show that titanium implant surfaces that mimic the physical properties of osteoclast resorption pits regulate cellular responses of bone marrow stromal cells (MSCs) by altering cell morphology, transcriptomes, and local factor production to increase their differentiation into osteoblasts without osteogenic media supplements required for differentiation of MSCs on tissue culture polystyrene (TCPS). The goal of this study was to determine how cells in contact with biomimetic implant surfaces regulate the microenvironment around these surfaces in vitro. Two different approaches were used. First, unidirectional signaling was assessed by treating human MSCs grown on TCPS with conditioned media from MSC cultures grown on Ti6Al4V biomimetic surfaces. In the second set of studies, bidirectional signaling was assessed by coculturing MSCs grown on mesh inserts that were placed into culture wells in which MSCs were grown on the biomimetic Ti6Al4V substrates. The results show that biomimetic Ti6Al4V surface properties induce MSCs to produce factors within 7 days of culture that stimulate MSCs not in contact with the surface to exhibit an osteoblast phenotype via endogenous BMP2 acting in a paracrine signaling manner.

The moonlighting activities of dihydrolipoamide dehydrogenase: Biotechnological and biomedical applications

Dihydrolipoamide dehydrogenase (DLDH) is a homodimeric flavin-dependent enzyme that catalyzes the NAD⁺ -dependent oxidation of dihydrolipoamide. The enzyme is part of several multi-enzyme complexes such as the Pyruvate Dehydrogenase system that transforms pyruvate into acetyl-co-A. Concomitantly with its redox activity, DLDH produces Reactive Oxygen Species (ROS), which are involved in cellular apoptotic processes. DLDH possesses several moonlighting functions. One of these is the capacity to adhere to metal-oxides surfaces. This was first exemplified by the presence of an exocellular form of the enzyme on the cell-wall surface of Rhodococcus ruber. This capability was evolutionarily conserved and identified in the human, mitochondrial, DLDH. The enzyme was modified with Arg-Gly-Asp (RGD) groups, which enabled its interaction with integrin-rich cancer cells followed by "integrin-assisted-endocytosis." This allowed harnessing the enzyme for cancer therapy. Combining the TiO₂ -binding property with DLDH's ROS-production, enabled us to develop several medical applications including improving oesseointegration of TiO₂ -based implants and photodynamic treatment for melanoma. The TiO₂ -binding sites of both the bacterial and human DLDH's were identified on the proteins' molecules at regions that overlap with the binding site of E3-binding protein (E3BP). This protein is essential in forming the multiunit structure of PDC. Another moonlighting activity of DLDH, which is described in this Review, is its DNA-binding capacity that may affect DNA chelation and shredding leading to apoptotic processes in living cells. The typical ROS-generation by DLDH, which occurs in association with its enzymatic activity and its implications in cancer and apoptotic cell death are also discussed.

Focal adhesion dynamics in cellular function and disease

Acting as a bridge between the cytoskeleton of the cell and the extra cellular matrix (ECM), the cell-ECM adhesions with integrins at their core, play a major role in cell signalling to direct mechanotransduction, cell migration, cell cycle progression, proliferation, differentiation, growth and repair. Biochemically, these adhesions are composed of diverse, yet an organised group of structural proteins, receptors, adaptors, various enzymes including protein kinases, phosphatases, GTPases, proteases, etc. as well as scaffolding molecules. The major integrin adhesion complexes (IACs) characterised are focal adhesions (FAs), invadosomes (podosomes and invadopodia), hemidesmosomes (HDs) and reticular adhesions (RAs). The varied composition and regulation of the IACs and their signalling, apart from being an integral part of normal cell survival, has been shown to be of paramount importance in various developmental and pathological processes. This review per-illustrates the recent advancements in the research of IACs, their crucial roles in normal as well as diseased states. We have also touched on few of the various methods that have been developed over the years to visualise IACs, measure the forces they exert and study their signalling and molecular composition. Having such pertinent roles in the context of various pathologies, these IACs need to be understood and studied to develop therapeutical targets. We have given an update to the studies done in recent years and described various techniques which have been applied to study these structures, thereby, providing context in furthering research with respect to IAC targeted therapeutics.

Vimentin regulates the assembly and function of matrix adhesions

The intermediate filament protein vimentin is a widely used phenotypic marker for identifying cells of the mesenchymal linkage such as fibroblasts and myofibroblasts, but the full repertoire of vimentin's functional attributes has not been fully explored. Here we consider how vimentin, in addition to its contributions to mechanical stabilization of cell structure, also helps to control the assembly of cell adhesions and migration through collagen matrices. While the assembly and function of matrix adhesions are critical for the differentiation of myofibroblasts and many other types of adherent cells, a potential mechanism that explains how vimentin affects the recruitment and abundance of centrally important proteins in cell adhesions has been elusive. Here we review recent data indicating that vimentin plays a central regulatory role in the assembly of focal adhesions which form in response to the attachment to collagen. We show that in particular, vimentin is a key organizer of the β1 integrin adhesive machinery, which affects cell migration through collagen. This review provides a comprehensive picture of the surprisingly broad array of processes and molecules with which vimentin interacts to affect cell function in the context of fibroblast and myofibroblast adhesion and migration on collagen.

RGD-Binding Integrins Revisited: How Recently Discovered Functions and Novel Synthetic Ligands (Re-)Shape an Ever-Evolving Field

Integrins have been extensively investigated as therapeutic targets over the last decades, which has been inspired by their multiple functions in cancer progression, metastasis, and angiogenesis as well as a continuously expanding number of other diseases, e.g., sepsis, fibrosis, and viral infections, possibly also Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV-2). Although integrin-targeted (cancer) therapy trials did not meet the high expectations yet, integrins are still valid and promising targets due to their elevated expression and surface accessibility on diseased cells. Thus, for the future successful clinical translation of integrin-targeted compounds, revisited and innovative treatment strategies have to be explored based on accumulated knowledge of integrin biology. For this, refined approaches are demanded aiming at alternative and improved preclinical models, optimized selectivity and pharmacological properties of integrin ligands, as well as more sophisticated treatment protocols considering dose fine-tuning of compounds. Moreover, integrin ligands exert high accuracy in disease monitoring as diagnostic molecular imaging tools, enabling patient selection for individualized integrin-targeted therapy. The present review comprehensively analyzes the state-of-the-art knowledge on the roles of RGD-binding integrin subtypes in cancer and non-cancerous diseases and outlines the latest achievements in the design and development of synthetic ligands and their application in biomedical, translational, and molecular imaging approaches. Indeed, substantial progress has already been made, including advanced ligand designs, numerous elaborated pre-clinical and first-in-human studies, while the discovery of novel applications for integrin ligands remains to be explored.

Structural integrity with functional plasticity: what type I IFN receptor polymorphisms reveal

The type I IFNs activate an array of signaling pathways, which are initiated after IFNs bind their cognate receptors, IFNα/β receptor (IFNAR)1 and IFNAR2. These signals contribute to many aspects of human health including defense against pathogens, cancer immunosurveillance, and regulation of inflammation. How these cytokines interact with their receptors influences the quality of these signals. As such, the integrity of receptor structure is pivotal to maintaining human health and the response to immune stimuli. This review brings together genome wide association studies and clinical reports describing the association of nonsynonymous IFNAR1 and IFNAR2 polymorphisms with clinical disease, including altered susceptibility to viral and bacterial pathogens, autoimmune diseases, cancer, and adverse reactions to live-attenuated vaccines. We describe the amino acid substitutions or truncations induced by these polymorphisms and, using the knowledge of IFNAR conformational changes, IFNAR-IFN interfaces and overall structure-function relationship of the signaling complexes, we hypothesize the effect of these polymorphisms on receptor structure. That these predicted changes to IFNAR structure are associated with clinical manifestations of human disease, highlights the importance of IFNAR structural integrity to maintaining functional quality of these receptor-mediated responses. Type I IFNs are pivotal to innate immune responses and ultimately, to human health. Understanding the consequences of altered structure on the actions of these clinically significant cell receptors provides important information on the roles of IFNARs in health and disease.

Minimal Residual Disease, Metastasis and Immunity

Progression from localized to metastatic disease requires cancer cells spreading to distant organs through the bloodstream. Only a small proportion of these circulating tumor cells (CTCs) survives dissemination due to anoikis, shear forces and elimination by the immune system. However, all metastases originate from CTCs capable of surviving and extravasating into distant tissue to re-initiate a tumor. Metastasis initiation is not always immediate as disseminated tumor cells (DTCs) may enter a non-dividing state of cell dormancy. Cancer dormancy is a reversible condition that can be maintained for many years without being clinically detectable. Subsequently, late disease relapses are thought to be due to cancer cells ultimately escaping from dormant state. Cancer dormancy is usually associated with minimal residual disease (MRD), where DTCs persist after intended curative therapy. Thus, MRD is commonly regarded as an indicator of poor prognosis in all cancers. In this review, we examine the current understanding of MRD and immunity during cancer progression to metastasis and discuss clinical perspectives for oncology.

Bearing My Heart: The Role of Extracellular Matrix on Cardiac Development, Homeostasis, and Injury Response

The extracellular matrix (ECM) is an essential component of the heart that imparts fundamental cellular processes during organ development and homeostasis. Most cardiovascular diseases involve severe remodeling of the ECM, culminating in the formation of fibrotic tissue that is deleterious to organ function. Treatment schemes effective at managing fibrosis and promoting physiological ECM repair are not yet in reach. Of note, the composition of the cardiac ECM changes significantly in a short period after birth, concurrent with the loss of the regenerative capacity of the heart. This highlights the importance of understanding ECM composition and function headed for the development of more efficient therapies. In this review, we explore the impact of ECM alterations, throughout heart ontogeny and disease, on cardiac cells and debate available approaches to deeper insights on cell–ECM interactions, toward the design of new regenerative therapies.

Measurement of Integrin Activation and Conformational Changes on the Cell Surface by Soluble Ligand and Antibody Binding Assays

Soluble ligand and conformation-dependent antibody binding assay of integrins on the cell surface is an effective approach to evaluate the activation status of integrins in live cells. The ligands or antibodies are usually labeled with biotin or a fluorescent dye and incubated with integrin-expressing cells in suspension. The cell-bound ligands and antibodies are then detected by flow cytometry. Here we describe the detailed protocols of soluble ligand or antibody binding assay for α_IIbβ₃, α_Vβ₃, α₅β₁, and α_Lβ₂ integrins that are transiently or stably expressed in the model cell lines such as HEK293 or CHO-k1 cells.

Functional Redundancy between β1 and β3 Integrin in Activating the IR/Akt/mTORC1 Signaling Axis to Promote ErbB2-Driven Breast Cancer

Integrin receptors coordinate cell adhesion to the extracellular matrix (ECM) to facilitate many cellular processes during malignant transformation. Despite their pro-tumorigenic roles, therapies targeting integrins remain limited. Here, we provide genetic evidence supporting a functional redundancy between β1 and β3 integrin during breast cancer progression. Although ablation of β1 or β3 integrin alone has limited effects on ErbB2-driven mammary tumorigenesis, deletion of both receptors resulted in a significant delay in tumor onset with a corresponding impairment in lung metastasis. Mechanistically, stiff ECM cooperates with integrin receptors to recruit insulin receptors (IRs) to focal adhesion through the formation of integrin/IR complexes, thereby preventing their lysosomal degradation. β1/β3 integrin-deficient tumors that eventually emerged exhibit impaired Akt/mTORC1 activity. Murine and human breast cancers exhibiting enhanced integrin-dependent activity also display elevated IR/Akt/mTORC1 signaling activity. Together, these observations argue that integrin/IR crosstalk transduces mechanical cues from the tumor microenvironment to promote ErbB2-dependent breast cancer progression.

Safety and Immunological Evaluation of Interleukin-21 Plus Anti-α4β7 mAb Combination Therapy in Rhesus Macaques

Human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infections compromise gut immunological barriers, inducing high levels of inflammation and a severe depletion of intestinal CD4+ T cells. Expression of α4β7 integrin promotes homing of activated T cells to intestinal sites where they become preferentially infected; blockade of α4β7 with an anti-α4β7 monoclonal antibody (mAb) prior to infection has been reported to reduce gut SIV viremia in rhesus macaques (RMs). Interleukin-21 (IL-21) administration in antiretroviral therapy-treated, SIV-infected RMs reduces gut inflammation and improves gut integrity. We therefore hypothesized that the combination of IL-21 and anti-α4β7 mAb therapies could synergize to reduce inflammation and HIV persistence. We co-administered two intravenous doses of rhesus anti-α4β7 mAb (50 mg/kg) combined with seven weekly subcutaneous infusions of IL-21-IgFc (100 μg/kg) in four healthy, SIV-uninfected RMs to evaluate the safety and immunological profiles of this intervention in blood and gut. Co-administration of IL-21 and anti-α4β7 mAb showed no toxicity at the given dosages as assessed by multiple hematological and chemical parameters and did not alter the bioavailability of the therapeutics or result in the generation of antibodies against the anti-α4β7 mAb or IL-21-IgFc. Upon treatment, the frequency of CD4 memory T cells expressing β7 increased in blood and decreased in gut, consistent with an inhibition of activated CD4 T-cell homing to the gut. Furthermore, the frequency of T cells expressing proliferation and immune activation markers decreased in blood and, more profoundly, in gut. The combined IL-21 plus anti-α4β7 mAb therapy is well-tolerated in SIV-uninfected RMs and reduces the gut homing of α4β7+ CD4 T cells as well as the levels of gut immune activation.

Beyond thrombosis: the impact of tissue factor signaling in cancer

Tissue factor (TF) is the primary initiator of the coagulation cascade, though its effects extend well beyond hemostasis. When TF binds to Factor VII, the resulting TF:FVIIa complex can proteolytically cleave transmembrane G protein-coupled protease-activated receptors (PARs). In addition to activating PARs, TF:FVIIa complex can also activate receptor tyrosine kinases (RTKs) and integrins. These signaling pathways are utilized by tumors to increase cell proliferation, angiogenesis, metastasis, and cancer stem-like cell maintenance. Herein, we review in detail the regulation of TF expression, mechanisms of TF signaling, their pathological consequences, and how it is being targeted in experimental cancer therapeutics.

Super-resolution Surface-Enhanced Raman Scattering Imaging of Single Particles in Cells

The ability to locate and identify molecular interactions in cells has significant importance for understanding protein function and molecular biology. Functionalized metallic nanoparticles have been used as probes for protein tracking and drug delivery because of their ability to carry therapeutic agents and readily functionalized surfaces. In this work, we present a super-resolution surface-enhanced Raman scattering (SERS) approach for imaging and tracking membrane receptors interacting with peptide-functionalized gold nanostars (AuNS). The αvβ3 integrin receptors in colon cancer cells are successfully targeted and imaged using AuNS with the high-affinity amino acid sequence arginine-glycine-aspartic acid-phenylalanine-cysteine (RGDFC) attached. The RGDFC peptide interaction with the integrin receptor provides a bright and fluctuating SERS signal that can be analyzed with localization microscopy algorithms. Additionally, the observed SERS spectrum is used to confirm protein-peptide interaction. Experiments with functionalized and bare AuNS illustrate specific and nonspecific binding events. Specific binding is monitored with a localization precision of ∼6 nm. The observed spatial resolution is associated with tight binding, which was confirmed by the slower diffusion coefficient measured from 4.4 × 10-11 cm2/s for the AuNS-RGDFC compared to 7.8 × 10-10 cm2/s for the bare AuNS. Super-resolution SERS images at different focal planes show evidence of internalized particles and suggest insights into protein orientation on the surface of cells. Our work demonstrates super-resolution SERS imaging to probe membrane receptor interactions in cells, providing chemical information and spatial resolution with potential for diverse applications in life science and biomedicine.

Inevitable role of TGF-β1 in progression of nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is a major health concern and the most commonly diagnosed chronic liver manifestation among 25% worldwide population. Obesity, insulin resistance, accumulation of toxic lipid free radicals, generation of oxidative stress, overconsumption of fat containing dietary meals and lack of exercise are the paramount factors accountable for the development of NAFLD. During NAFLD, increased oxidative stress and production of enormous number of toxic free radicals activates a number of pro-inflammatory and inflammatory pathways. TGF-β signaling mechanisms play a central role in maintaining the normal homeostasis of liver. TGF-β1, one of the three isoforms of TGF-β family has significant role in different stages of chronic liver conditions. TGF-β1 promotes HSC activation and extracellular matrix production (ECM), which further contributes in the progression of NAFLD. In this review, we outline the role of TGF-β1 in different phases of progressive NAFLD along with the signaling mechanism.

Cell matrix adhesion in cell migration

The ability of cells to migrate is a fundamental physiological process involved in embryonic development, tissue homeostasis, immune surveillance and wound healing. In order for cells to migrate, they must interact with their environment using adhesion receptors, such as integrins, and form specialized adhesion complexes that mediate responses to different extracellular cues. In this review, we discuss the role of integrin adhesion complexes (IACs) in cell migration, highlighting the layers of regulation that are involved, including intracellular signalling cascades, mechanosensing and reciprocal feedback to the extracellular environment. We also discuss the role of IACs in extracellular matrix remodeling and how they impact upon cell migration.

Self-Assembly of Integrin Ligands on the Apical Membrane Inhibits the Migration of Glioma Cells

Malignant brain cancer remains challenging in treatment due to the highly invasive quality of gliomas. Inspired by the upregulated expression of integrin β1 subunits in tumors, we designed and synthesized an integrin-targeting self-assembling ligand based on a laminin-derived peptide that selectively forms nanofibrous microdomains on the apical membrane of glioma cells, inhibiting their migration and invasion.

The EGFL7-ITGB3-KLF2 axis enhances survival of multiple myeloma in preclinical models

Angiogenic factors play a key role in multiple myeloma (MM) growth, relapse, and drug resistance. Here we show that malignant plasma cells (cell lines and patient-derived MM cells) express angiocrine factor EGF like-7 (EGFL7) mRNA and protein. MM cells both produced EGFL7 and expressed the functional EGFL7 receptor integrin β 3 (ITGB3), resulting in ITGB3 phosphorylation and focal adhesion kinase activation. Overexpression of ITGB3 or EGFL7 enhanced MM cell adhesion and proliferation. Intriguingly, ITGB3 overexpression upregulated the transcription factor Krüppel-like factor 2 (KLF2), which further enhanced EGFL7 transcription in MM cells, thereby establishing an EGFL7-ITGB3-KLF2-EGFL7 amplification loop that supports MM cell survival and proliferation. EGFL7 expression was found in certain plasma cells of patients with refractory MM and of patients at primary diagnosis. NOD.CB17-Prkdc/J mice transplanted with MM cells showed elevated human plasma EGFL7 levels. EGFL7 knockdown in patient-derived MM cells and treatment with neutralizing antibodies against EGFL7 inhibited MM cell growth in vitro and in vivo. We demonstrate that the standard-of-care MM drug bortezomib upregulates EGFL7, ITGB3, and KLF2 expression in MM cells. Inhibition of EGFL7 signaling in synergy with BTZ may provide a novel strategy for inhibiting MM cell proliferation.

VLA-4 Expression and Activation in B Cell Malignancies: Functional and Clinical Aspects

Lineage commitment and differentiation of hematopoietic cells takes place in well-defined microenvironmental surroundings. Communication with other cell types is a vital prerequisite for the normal functions of the immune system, while disturbances in this communication support the development and progression of neoplastic disease. Integrins such as the integrin very late antigen-4 (VLA-4; CD49d/CD29) control the localization of healthy as well as malignant B cells within the tissue, and thus determine the patterns of organ infiltration. Malignant B cells retain some key characteristics of their normal counterparts, with B cell receptor (BCR) signaling and integrin-mediated adhesion being essential mediators of tumor cell homing, survival and proliferation. It is thus not surprising that targeting the BCR pathway using small molecule inhibitors has proved highly effective in the treatment of B cell malignancies. Attenuation of BCR-dependent lymphoma–microenvironment interactions was, in this regard, described as a main mechanism critically contributing to the efficacy of these agents. Here, we review the contribution of VLA-4 to normal B cell differentiation on the one hand, and to the pathophysiology of B cell malignancies on the other hand. We describe its impact as a prognostic marker, its interplay with BCR signaling and its predictive role for novel BCR-targeting therapies, in chronic lymphocytic leukemia and beyond.