Thrombospondin-1 (THBS1/P07996) – Function, Processes, and Localization OpenAI o3-deep-research-2025-06-26 107 citations 2025-11-04T01:42:12.748529

Thrombospondin-1 (THBS1/P07996) – Function, Processes, and Localization

Introduction and Gene Overview

THBS1 encodes thrombospondin-1 (TSP1), a large secreted glycoprotein that plays regulatory rather than purely structural roles in the extracellular matrix (ECM) (link.springer.com) (www.genome.jp). TSP1 was originally discovered in platelets and belongs to the matricellular protein family – secreted factors that modulate cell–matrix interactions, cytokine activity, and receptor signaling without forming major structural fibers (link.springer.com). In humans, TSP1 is highly conserved and loss-of-function mutations are very rare, indicating critical importance. Deep exome analyses found far fewer inactivating mutations in THBS1 than expected (only 7 observed vs. ~56 predicted), giving THBS1 a pLI of 1.0 (highest loss-of-function intolerance) (link.springer.com). This contrasts with mice, where Thbs1 knockout is viable, suggesting that TSP1’s functions are essential for human survival under environmental stresses (link.springer.com) (link.springer.com). THBS1 is broadly expressed (low tissue specificity) with notable protein-level expression in platelets and certain immune cells (e.g. dendritic cells) (www.genome.jp). Overall, thrombospondin-1 is an adhesive, multi-functional ECM protein that orchestrates cell–cell and cell–matrix communication in processes such as angiogenesis, inflammation, and tissue repair (www.genome.jp).

Structure and Localization of Thrombospondin-1

Human TSP1 is a homotrimeric protein ~450 kDa in size, composed of three identical ~150 kDa subunits. Each TSP1 monomer is modular, containing multiple domains that enable diverse interactions (www.genome.jp). The N-terminal domain is a globular region responsible for binding glycosaminoglycans (heparan sulfate) and certain receptors. For example, this N-terminal region can bind cell-surface calreticulin (with co-receptor LRP1) and integrins, mediating cell adhesion and uptake/clearance of TSP1 (pmc.ncbi.nlm.nih.gov). A short coiled-coil segment near the N-terminus allows the three monomers to assemble via interchain disulfide bonds. Just downstream, TSP1 contains three type 1 repeats (TSRs) – unique peptide modules (each ~60 amino acids) originally called properdin repeats. These TSRs are critical for TSP1’s interactions with other proteins: they harbor the WSXW motifs that bind the receptor CD36 and a conserved LSKL sequence that binds latent TGF-β (discussed below). Following the TSRs, TSP1 has three type 2 repeats (EGF-like repeats) and a set of type 3 repeats, which are calcium-binding loops. Notably, the type 3 region contains an RGD sequence that can be recognized by integrins (e.g. α_vβ₃), though this site’s accessibility is regulated by disulfide bonds (www.mdpi.com). At the C-terminus, TSP1 has a globular cell-binding domain that mediates interactions with cell surface receptors including CD47 (also known as integrin-associated protein) (www.genome.jp) (pmc.ncbi.nlm.nih.gov). This multi-domain architecture equips thrombospondin-1 to bind numerous ligands and receptors simultaneously, effectively serving as an ECM scaffold and signaling hub.

Subcellular localization: TSP1 is a secreted protein that predominantly functions in the extracellular space and matrix (www.genome.jp). It is synthesized with a signal peptide for the secretory pathway and is released from cells into the ECM or circulation. Within tissues, TSP1 often associates with the ECM and cell surfaces by binding to proteoglycans and integrins (pmc.ncbi.nlm.nih.gov). Platelets are a major storage site: TSP1 is loaded in platelet α-granules and is secreted upon platelet activation (e.g. by thrombin) (www.genome.jp). Once released, TSP1 can bind to other matrix components (like fibrinogen, fibronectin, and collagens) and cluster on cell surfaces in a Ca²⁺-dependent manner (www.genome.jp). This localized extracellular presence is crucial for its role as a mediator between cells and their microenvironment. There is also evidence that cell-surface receptors (like LRP1) can internalize TSP1 for turnover, but its primary site of action is outside the cell on the cell membrane or ECM.

Biological Functions and Mechanisms of TSP1

Thrombospondin-1 is a multifunctional regulator of cellular behavior. Rather than catalyzing a single biochemical reaction (it is not an enzyme), TSP1 serves as an adaptor protein and signaling modulator in the extracellular milieu. Through its various binding domains, TSP1 influences a broad spectrum of biological processes – from blood vessel growth to immune cell activation – often acting as a molecular bridge or antagonist in key signaling pathways (link.springer.com). Below we detail TSP1’s major functions, the mechanisms involved, and where these actions occur:

Angiogenesis Inhibition

One of the most prominent roles of TSP1 is as an endogenous inhibitor of angiogenesis (the formation of new blood vessels). TSP1 was first identified in 1990 as a potent angiogenesis inhibitor, sparking interest in its anti-cancer potential (www.mdpi.com). Thrombospondin-1 directly suppresses endothelial cell proliferation, migration, and survival, thereby blocking the growth of new capillaries (www.mdpi.com). It can even induce endothelial apoptosis when present at sufficient levels (www.mdpi.com). Mechanistically, this anti-angiogenic effect is mediated by specific interactions on the surface of endothelial cells. In particular, TSP1’s type-1 repeats engage the receptor CD36 on microvascular endothelium (www.mdpi.com). Binding of TSP1 to CD36 triggers a signaling cascade (involving the Fyn tyrosine kinase and p38 MAPK, as shown in earlier studies) that leads to endothelial cell apoptosis and growth arrest. Consistent with this, CD36 was the first identified TSP1 receptor required for its angiogenesis-inhibitory activity (www.mdpi.com). Small peptide mimetics derived from the TSP1 TSR sequence that binds CD36 (e.g. the 2nd TSR’s RFYVVM motif) have demonstrated anti-angiogenic effects in preclinical tumor models (www.mdpi.com). Some of these peptides (e.g. ABT-510) even advanced to clinical trials as anti-cancer agents, although they did not achieve significant efficacy in human studies (www.mdpi.com).

Beyond the CD36 pathway, TSP1 inhibits angiogenesis through sequestration and neutralization of pro-angiogenic factors. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF-2) are key growth factors that stimulate blood vessel formation. TSP1 can bind directly to VEGF and FGF-2, preventing these factors from effectively engaging their receptors on endothelial cells (www.mdpi.com). By acting as a sink for pro-angiogenic cytokines, TSP1 further tilts the balance toward vessel growth suppression. TSP1 also interacts with platelet-derived growth factor (PDGF), and this interaction has been reported to modulate recruitment of cells like pericytes during angiogenesis (www.mdpi.com). In tissues, these combined actions make TSP1 a critical break on neovascularization. For example, tumors often downregulate THBS1 expression to evade its anti-angiogenic influence, and loss of TSP1 in the tumor stroma is associated with more robust angiogenesis and tumor progression (www.mdpi.com). Conversely, in normal physiology, TSP1 is upregulated during wound healing and other contexts where unchecked vessel growth needs to be curtailed once initial repair is done (www.mdpi.com). Notably, Thbs1-null mice confirmed TSP1’s angiogenic role: they show an exaggerated blood vessel response under certain stresses, although in simple wound models TSP1’s function was more nuanced (as it also affects inflammation and repair, see below) (www.mdpi.com). Overall, by binding endothelial receptors (CD36) and growth factors (VEGF, FGF-2), TSP1 acts extracellularly to enforce an anti-angiogenic signaling environment, restraining new blood vessel formation.

Activation of Latent TGF-β1 and Growth Factor Regulation

Thrombospondin-1 plays a pivotal role in the TGF-β (transforming growth factor beta) pathway by converting TGF-β from its latent to active form. TGF-β1 is secreted as part of a latent complex (with latency-associated peptide, LAP, and latent TGF-β binding proteins) that keeps it inactive. TSP1 can bind to the latent TGF-β1 complex via sequences in its type-1 repeats, and this interaction induces a conformational change that releases active TGF-β1 (link.springer.com). The ability of TSP1 to activate latent TGF-β1 was first demonstrated in the late 1990s: Crawford et al. (1998) showed that TSP1 is necessary to activate TGF-β1 in vivo, explaining certain phenotypes of TSP1-null mice (link.springer.com). In Thbs1^−/− knockout mice, failure to activate TGF-β1 led to an unchecked inflammatory response – for example, young Thbs1-null mice developed chronic lung inflammation that was attributable to loss of TSP1-mediated TGF-β activation (link.springer.com). In normal mice, TSP1 activates TGF-β1 in the lung, increasing active TGF-β1 levels which suppress inflammation and maintain immune homeostasis (link.springer.com). This is a critical function of TSP1 in tissues: as TGF-β1 is a potent immunosuppressive and pro-fibrotic cytokine, TSP1 serves as an upstream controller that modulates TGF-β bioavailability. Indeed, when TSP1 is absent, not only inflammation but also certain tissue repair processes are altered. For instance, studies found that administering a TSP1-derived peptide (LSKL) that blocks TSP1–TGFβ interaction can reduce fibrosis in injury models, underlining TSP1’s role in driving TGF-β activation in fibrosis (link.springer.com).

Beyond TGF-β1, TSP1 can bind other growth factors or cytokines. It has affinity for vascular endothelial growth factor (VEGF) as noted, and can bind fibroblast growth factor-2, which affects not just angiogenesis but also general tissue remodeling (www.mdpi.com). TSP1 may also indirectly influence connective tissue growth factor (CTGF/CCN2): in a bleomycin-induced lung injury model, TSP1 limited tissue damage and was associated with reduced CTGF expression and collagen deposition, suggesting that TSP1’s activation of TGF-β (which can induce CTGF) is context-dependent and tightly regulated (link.springer.com). In summary, thrombospondin-1’s type-1 repeat domains provide a mechanism to activate latent TGF-β1 in the ECM (link.springer.com). Through this mechanism, TSP1 influences pathways of inflammation, immune tolerance, and fibrosis, since TGF-β1 signaling affects immune cell differentiation (e.g. promoting regulatory T-cells), extracellular matrix production, and resolution of inflammatory responses. This function is extracellular – TSP1 and latent TGF-β interact in the ECM or on cell surfaces, after TSP1 is secreted. By controlling a major cytokine’s activation state, TSP1 essentially links cell injury or stress signals (that induce TSP1 expression) to the TGF-β–driven healing and immune modulation response.

Cell Adhesion and ECM Remodeling

As an adhesive glycoprotein, thrombospondin-1 also contributes to cell–matrix and cell–cell adhesion dynamics. TSP1 can bind various matrix components and cell receptors to influence how cells attach, migrate, or organize in the tissue. For example, the N-terminal domain of TSP1 binds to glycosaminoglycans (e.g. heparan sulfate proteoglycans) in the matrix, effectively anchoring TSP1 to cell surfaces or the ECM (pmc.ncbi.nlm.nih.gov). Through this anchorage, TSP1 can present other binding sites to cells. Integrins are one set of receptors that interact with TSP1: the presence of an RGD sequence in TSP1’s type 3 repeats allows binding to integrins like α_vβ₃ (though under redox control) (www.mdpi.com), and other regions of TSP1 can engage integrin α₄β_{1】 and α_IIbβ_{3 (on platelets) as shown in various studies. By binding integrins, TSP1 can mediate cell adhesion to the matrix and influence signal transduction from the ECM. Interestingly, TSP1’s N-terminal domain also binds to a complex of calreticulin (a surface-expressed chaperone) with LDL-receptor–related protein-1 (LRP1). This calreticulin/LRP1/TSP1 interaction can trigger focal adhesion disassembly and cell motility, as shown in fibroblasts – essentially, TSP1 engagement causes cells to release from substratum and migrate, an activity requiring its N-terminal/collagen-like domain and the cell’s endocytic receptors (pmc.ncbi.nlm.nih.gov). Thus, TSP1 can have pro-migratory effects by modulating adhesion sites. In the ECM remodeling context, TSP1 has been reported to bind matrix proteases and protease inhibitors – for instance, it can bind MMP2 proenzyme and tissue inhibitor TIMP-2, localizing them on the ECM and regulating proteolytic activity. In a microbial infection model, TSP1 protected tissues from proteolytic damage by inhibiting proteases: in Pseudomonas-infected lungs, TSP1 limited pathogen and host protease activity, reducing injury (link.springer.com). These findings illustrate a broader structural/adaptor role: TSP1 organizes molecular complexes in the pericellular space, affecting cell adhesion, migration, and matrix turnover. Notably, platelet aggregation is partly facilitated by TSP1’s adhesive function: TSP1 can bind fibrinogen and fibronectin, helping to crosslink platelets during clot formation (pmc.ncbi.nlm.nih.gov). This occurs when TSP1 is released from platelet granules into a forming clot, where it binds fibrin/fibrinogen matrices and platelet integrins, thereby stabilizing platelet plugs. In summary, thrombospondin-1 acts as an extracellular “glue” and organizer, connecting cells to the matrix and concentrating molecules (integrins, proteases, growth factors) to specific sites, which is essential for connective tissue organization and wound repair (link.springer.com).}}

Regulation of Nitric Oxide Signaling and Vascular Tone

Thrombospondin-1 is a significant regulator of vasoactive signaling, particularly through its receptor CD47. Work by Isenberg, Roberts, and colleagues uncovered that TSP1–CD47 signaling antagonizes nitric oxide (NO)–cGMP signaling in vascular cells (link.springer.com). NO is a key endothelium-derived relaxing factor that binds and activates soluble guanylate cyclase in smooth muscle and platelets, raising cGMP to induce vasodilation and inhibit platelet activation. TSP1 binding to CD47 effectively blocks this pathway. Specifically, when TSP1 engages CD47 on endothelial cells, smooth muscle cells, or platelets, it inhibits NO-stimulated cGMP production and downstream signaling (link.springer.com). This occurs through CD47-dependent signaling that interferes with NO receptor activation and may promote degradation of the NO signaling components. Functionally, this means TSP1 can cause vasoconstriction and make platelets and vessels less responsive to NO. Indeed, experiments showed that blood vessels or platelets from Thbs1^−/− or Cd47^−/− mice have enhanced responses to NO (greater vasodilation, less platelet aggregation), whereas adding TSP1 blunts those responses (link.springer.com) (www.mdpi.com).

The physiological consequence of TSP1’s anti-NO signaling is context-dependent. In acute injury, this function is protective: TSP1 is rapidly released by platelets at wound sites and acts as a potent vasoconstrictor, helping to limit bleeding and promote hemostasis (www.mdpi.com). By constricting damaged blood vessels and making platelets more aggregable (less inhibited by NO), TSP1 via CD47 aids in clot stabilization (www.mdpi.com). Consistently, TSP1 is considered an autocrine factor in platelets that reinforces platelet activation and clot formation upon vascular injury (www.mdpi.com). However, in ischemic conditions (e.g. after a heart attack or in ischemic tissue wounds), TSP1’s vasoconstrictive action can be detrimental – it limits blood flow and tissue perfusion when more circulation would be beneficial (www.mdpi.com). This duality was seen in experiments: Thbs1-null mice recover better from certain ischemic injuries (due to unopposed NO signaling and better blood perfusion), yet they might bleed more without TSP1’s acute hemostatic effect (www.mdpi.com) (www.mdpi.com). Thus, TSP1 is a critical regulator of vascular tone and perfusion, exerting its effects outside the cell by binding CD47 on the cell surface. Notably, CD47 shares TSP1’s loss-of-function intolerance in humans (pLI ~0.9), suggesting evolutionary pressure to maintain this NO-inhibitory pathway for survival (link.springer.com) (link.springer.com). In summary, through the TSP1–CD47 axis, thrombospondin-1 integrates with the nitric oxide signaling pathway, inhibiting vasodilatory signals and promoting vasoconstriction and thrombosis as needed in vascular homeostasis (www.mdpi.com) (www.mdpi.com).

Immune Modulation and Inflammation

Thrombospondin-1 also modulates the immune system, with effects on both innate and adaptive immunity. Some of these effects are mediated by the pathways discussed above (TGF-β activation and NO signaling), while others involve direct cell–cell interactions. Active TGF-β1 generated by TSP1 can promote immune tolerance by driving the differentiation of regulatory T cells and suppressing effector T-cell activation, as well as by inhibiting excessive inflammatory responses (link.springer.com). This is exemplified by the Thbs1^−/− mouse’s inflammatory lung phenotype, which was rescued by restoring TGF-β activity (link.springer.com). In addition, TSP1’s interaction with CD47 influences immune cell behavior. CD47 is expressed on many immune cells and often functions as a “do-not-eat-me” signal by interacting with SIRPα on phagocytes. Binding of TSP1 to CD47 on T cells, dendritic cells, or NK cells can transmit signals that alter their activity. Studies have found that TSP1–CD47 signaling tends to dampen T-cell and NK cell activation, thereby limiting anti-tumor and anti-microbial immunity (www.mdpi.com) (link.springer.com). For instance, in cancer models, TSP1 is known to limit antitumor immunity: it can inhibit T-cell proliferation and cytotoxicity and also affect NK cell function via CD47, creating a more immunosuppressive tumor microenvironment (www.mdpi.com). Conversely, mice lacking TSP1 or CD47 show enhanced T-cell responses in some contexts, but they may also be more susceptible to certain infections due to dysregulated inflammation (link.springer.com) (link.springer.com). The net effect of TSP1 on immunity appears context-specific: it can either protect against overzealous inflammation (as in preventing immunopathology in infection or autoimmunity) or impede effective immune clearance (as in anti-tumor immunity).

TSP1 also affects innate immune cells such as macrophages. It is reported to bind CD36 on macrophages and synergize with Toll-like receptors, potentially enhancing inflammasome activation in sterile inflammation contexts (insight.jci.org). A recent study in kidney ischemia-reperfusion injury showed TSP1 interacting with CD36 on renal tubular cells and macrophages to amplify IL-1β production and inflammation (insight.jci.org) (insight.jci.org). Additionally, TSP1 can be released by immune cells themselves: for example, dendritic cells secrete TSP1, which then can act in an autocrine or paracrine manner to influence cell maturation and T-cell priming. In summary, TSP1 is a modulator of immune responses, operating largely in the extracellular space to control cytokine activation (e.g. TGF-β), to engage inhibitory receptors (CD47, CD36) on immune cells, and to shape the inflammatory milieu. These activities contribute to its role in regulating inflammation, host defense, and tissue immune privilege (link.springer.com). For instance, during an infection or injury, TSP1 might help contain damage by activating TGF-β and reducing NO (thus limiting inflammation and oxidative stress), but during cancer or chronic disease, high TSP1 can contribute to immune evasion and persistent inflammation (see below).

Pathways and Interactions Summary

Thrombospondin-1 does not function in isolation; it sits at nexus of multiple signaling and structural pathways. To summarize key pathways involving TSP1:

Angiogenesis Pathway: TSP1 opposes the pro-angiogenic VEGF/FGF pathways by directly binding growth factors and by triggering apoptosis in endothelial cells via CD36 (www.mdpi.com) (www.mdpi.com). It also modulates PDGF signaling in vessel maturation (www.mdpi.com). In this way, TSP1 is part of the body’s system for negative regulation of angiogenesis.
TGF-β Activation: TSP1 is an activator in the TGF-β signaling pathway, binding latent TGF-β1 and releasing active cytokine (link.springer.com). This places TSP1 upstream of numerous TGF-β–mediated processes (fibrosis, immune regulation, cell growth inhibition).
NO–cGMP Signaling: Through CD47, TSP1 intersects with the nitric oxide signaling cascade, inhibiting NO’s effects on cGMP production in vascular cells (link.springer.com). Thus, TSP1 is a counter-regulator in pathways controlling vasodilation, blood flow, and platelet reactivity.
Integrin and Adhesion signaling: By binding integrins (α_vβ₃, α_IIbβ_{3>, etc.), TSP1 influences FAK and Src-family kinase signaling associated with cell adhesion and migration. Its interaction with calreticulin/LRP1 on cells triggers cytoskeletal signaling leading to focal adhesion turnover. These interactions tie TSP1 to pathways of cell motility and ECM remodeling.}
Immune signaling: TSP1 impacts immune cell receptor pathways – for example, signals through CD47 on T cells (which can modulate Ca²⁺ and cyclic nucleotide signals in those cells), and CD36/TLR in macrophages (affecting NF-κB and inflammasome pathways) (insight.jci.org). TSP1-activated TGF-β also feeds into Smad signaling in immune cells to promote regulatory phenotypes. Thus, TSP1 intersects with inflammatory signaling networks (e.g. NF-κB, NLRP3 inflammasome, TGF-β/Smad).

Importantly, these pathways do not act in isolation. For instance, in a wound-healing scenario, TSP1 is upregulated and simultaneously inhibits angiogenesis (via CD36), promotes clotting and vasoconstriction (via CD47), and activates TGF-β (via TSRs) to control scar formation and inflammation. These coordinated actions illustrate how TSP1 functions as a matricellular coordinator of complex biological responses (link.springer.com).

Current Research and Clinical Perspectives

Because of its central regulatory roles, THBS1/TSP1 has been a focus of both fundamental and translational research. Current developments (2023–2024) continue to uncover new dimensions of TSP1 function and potential clinical applications:

“Inflammaging” and Aging: A 2023 study identified TSP1 as a key driver of age-related chronic inflammation (inflammaging) in blood stem cells (pubmed.ncbi.nlm.nih.gov). Old hematopoietic stem cells show elevated Thbs1, and genetic or pharmacologic suppression of TSP1 improved stem cell function and reduced inflammatory cytokines, effectively prolonging hematopoietic healthspan in mice (pubmed.ncbi.nlm.nih.gov). This positions TSP1 as a promising target to mitigate age-associated immune decline.
Metabolic and Fibrotic Diseases: TSP1 has been implicated in metabolic syndrome (promoting adipose tissue inflammation and insulin resistance) (www.genome.jp) and in organ fibrosis (via TGF-β activation). For example, blocking TSP1–TGFβ interaction is being explored to treat fibrosis in kidneys, lungs, and liver (link.springer.com). Upregulated THBS1 is observed in fibrotic or inflammatory lesions, and animal models with Thbs1 knockout are protected in some settings of obesity-related inflammation and tissue fibrosis (www.genome.jp).
Cancer Therapy: Given its role in suppressing angiogenesis and immune surveillance in tumors, TSP1 is being studied as both a therapeutic target and a therapeutic agent. On one hand, downregulating TSP1 or blocking its receptors (like CD47) can boost anti-tumor immunity and blood flow to tumors; indeed, anti-CD47 antibodies are in clinical trials to stimulate macrophage-mediated tumor clearance (these trials were motivated in part by the knowledge that TSP1-CD47 signaling restrains immune attack on tumors) (www.mdpi.com). On the other hand, analogs of TSP1 have been tested to inhibit tumor angiogenesis – e.g., the TSP1-mimetic peptide ABT-510 was trialed in cancer patients to cut off tumor blood supply. While safe, these TSP1-mimetics had limited efficacy as single agents (www.mdpi.com), suggesting combination approaches or more potent formulations may be needed.
Cardiovascular Disease: THBS1 polymorphisms in humans have been linked to cardiovascular risk. A notable example is a THBS1 allele associated with early myocardial infarction and altered calcium-binding in TSP1 (link.springer.com). Elevated TSP1 is also found in atherosclerotic plaques and may influence plaque stability by regulating proteases and calling in inflammatory cells (via its chemoattractant domains for monocytes) (pmc.ncbi.nlm.nih.gov). Therapies aimed at TSP1-CD47 are being considered for improving tissue survival after heart attack or stroke by relieving TSP1’s brake on NO-mediated blood flow (www.mdpi.com).
Biomarker Potential: TSP1 is emerging as a biomarker for disease severity in certain conditions. For instance, a 2024 clinical study in acute-on-chronic liver failure (ACLF) identified THBS1 as the most upregulated gene in patients’ blood cells, with TSP1 levels closely correlating with inflammation and liver injury severity (pmc.ncbi.nlm.nih.gov). High plasma TSP1 predicted short-term mortality in ACLF (28-day AUROC ~0.74) (pmc.ncbi.nlm.nih.gov), highlighting its value as a prognostic marker. This makes sense given TSP1’s role in amplifying systemic inflammation; indeed, in ACLF models, TSP1 exacerbates inflammatory injury in the liver and TSP1 knockout mice were protected from liver damage (pmc.ncbi.nlm.nih.gov). Such findings underscore TSP1’s relevance not only as a functional player but also as an indicator of disease activity.

In summary, thrombospondin-1 (THBS1) is a versatile extracellular regulator with a well-defined primary role: it mediates cell–matrix interactions and modulates key signaling pathways (angiogenic, TGF-β, NO/cGMP) in the extracellular environment. Its action is largely outside the cell, where it binds to other proteins and receptors to influence processes like angiogenesis (inhibition), wound healing, immune regulation, and vascular homeostasis (link.springer.com). TSP1’s functions are supported by substantial experimental evidence, from molecular interaction studies to animal models, and even human genetic data. Authoritative reviews and studies (as of 2023) stress that while TSP1 is not required for basic development in mice, it becomes crucial under stress conditions – regulating bleeding, ischemia, and infection outcomes (link.springer.com) (www.mdpi.com). This explains why humans have evolved to strongly conserve THBS1. Its multifaceted roles in pathology also make it a target of interest for new therapies and a useful biomarker in inflammatory and vascular diseases. Continuing research is actively uncovering new mechanisms (like in aging and stem cell niches) for this protein, reaffirming thrombospondin-1 as a central extracellular “orchestrator” of cellular function in human biology (link.springer.com).

Sources:

Bornstein P. & Sage E. (2014). Matricellular proteins in cell-matrix communication. Matrix Biol. (Review) (link.springer.com) (link.springer.com).
Adams J.C. & Lawler J. (2004). The thrombospondin family: multifunctional regulators of cell interactions. J. Cell Sci. (Review) (www.genome.jp) (pmc.ncbi.nlm.nih.gov).
Lawler J. et al. (1998). Thrombospondin-1–null mice: inflammation and tissue homeostasis findings. J. Clin. Invest. (link.springer.com).
Crawford S.E. et al. (1998). Thrombospondin-1 enables latent TGF-β activation in vivo. J. Clin. Invest. (link.springer.com).
Isenberg J.S. et al. (2008). Thrombospondin-1/CD47 blocking of nitric oxide signaling modulates vascular responses. Proc. Natl. Acad. Sci. USA (link.springer.com).
Kaur S. et al. (2021). Functions of Thrombospondin-1 in the Tumor Microenvironment. Int. J. Mol. Sci. 22(9):4570 (www.mdpi.com) (www.mdpi.com).
Gao A.G. et al. (1996). TSP1 binds CD47 to regulate integrin-associated signaling. J. Biol. Chem. (www.genome.jp).
Jiménez B. et al. (2000). Signals through CD36 mediate TSP1’s anti-angiogenic effects. Nature Med. (www.genome.jp).
“Why do humans need thrombospondin-1?” – Roberts D.D. (2023). J. Cell Commun. Signal. 17:485–493 (Review) (link.springer.com) (link.springer.com).
BMC Medicine (2024). THBS1 as biomarker in acute-on-chronic liver failure. BMC Med. 22:95 (pmc.ncbi.nlm.nih.gov). (Plus additional references within text)

Citations

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