CD93

Official Full Name

CD93 molecule

Organism

Homo sapiens

GeneID

22918

Background

The protein encoded by this gene is a cell-surface glycoprotein and type I membrane protein that was originally identified as a myeloid cell-specific marker. The encoded protein was once thought to be a receptor for C1q, but now is thought to instead be involved in intercellular adhesion and in the clearance of apoptotic cells. The intracellular cytoplasmic tail of this protein has been found to interact with moesin, a protein known to play a role in linking transmembrane proteins to the cytoskeleton and in the remodelling of the cytoskeleton. [provided by RefSeq, Jul 2008]

Synonyms

C1QR1; C1qRP; CDw93; ECSM3; MXRA4; C1qR(P); dJ737E23.1;

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Detailed Information

The CD93 gene, located on human chromosome 20p11.21, encodes a type I transmembrane glycoprotein. Initially identified as a myeloid cell-specific surface marker and proposed as a receptor for complement component C1q (hence the name C1qRp), subsequent studies have redefined its role primarily in cell adhesion and clearance of apoptotic cells.

Structurally, CD93 possesses a distinctive extracellular region comprising a C-type lectin-like domain, multiple EGF-like repeats, and a heavily glycosylated mucin-like domain, suggesting its involvement in protein–protein and protein–carbohydrate interactions. Its relatively short intracellular domain interacts with moesin, a member of the ERM (ezrin-radixin-moesin) family, which links membrane proteins to the actin cytoskeleton, providing structural support for cell morphology and motility. CD93 expression is not limited to myeloid cells; it is highly expressed on endothelial cells, particularly activated and proliferating vascular endothelium, highlighting its potential importance in vascular biology.

Biological Significance

CD93 exhibits multifaceted biological functions, primarily centered on innate immune regulation and angiogenesis. In the immune system, CD93 acts as a functional receptor for opsonins including C1q, mannose-binding lectin, and surfactant protein A. These molecules mark apoptotic cells or immune complexes, and CD93 recognition enhances phagocytic uptake by macrophages and other phagocytes, promoting efficient clearance of apoptotic cells. This process is crucial for homeostasis, preventing release of intracellular toxins and autoimmune activation.

Figure 1. The CD93 signaling pathway in migrating endothelial cells. (Barbera S, et al., 2021)

In vascular biology, CD93 is a marker of endothelial activation and actively promotes angiogenesis. Mechanistically, CD93 interacts with β-dystroglycan, recruiting and activating SRC kinase, leading to CBL adaptor phosphorylation and formation of docking platforms for downstream molecules such as CRKL, ultimately driving endothelial cell migration, a key step in neovascularization. Recent studies also identified CD93 as the endothelial receptor for extracellular matrix glycoproteins multimerin-2 (MMRN2) and IGFBP7, which regulate cell adhesion, spreading, and tubular structure formation. Furthermore, CD93 modulates VEGFR2 signaling, influencing endothelial barrier integrity. Collectively, CD93 functions as a cell-surface integrator, coordinating extracellular matrix signals with cytoskeletal rearrangements to regulate immune clearance and tissue remodeling.

Clinical Relevance

CD93's clinical relevance is increasingly recognized, particularly as a biomarker and therapeutic target in vascular diseases and oncology. In tumors, CD93 plays a central role in tumor angiogenesis, making it an attractive anti-angiogenic target. Elevated CD93 expression on endothelial cells is observed in glioblastoma, colorectal cancer, and lung cancer, often correlating with poor prognosis. Preclinical studies show that monoclonal antibody blockade or gene silencing of CD93 inhibits tumor vascularization, causing tumor necrosis and growth restriction, supporting its potential as a therapeutic target. Given resistance issues with VEGF-targeted therapies, CD93-targeted interventions offer a promising complementary or alternative angiogenesis strategy.

Beyond oncology, CD93 may contribute to pathological angiogenesis in conditions such as atherosclerosis and diabetic retinopathy. Its role in apoptotic cell clearance also suggests potential links to autoimmune diseases like systemic lupus erythematosus, where defective clearance triggers autoimmune activation. While no CD93-targeted therapies have yet entered clinical use, ongoing studies exploring its interaction with MMRN2 and IGFBP7 may enable future interventions for abnormal angiogenesis or immune dysregulation. Additionally, soluble CD93 levels in serum are being investigated as a biomarker of endothelial activation and inflammatory disease activity. Overall, CD93 represents a multifunctional interface between innate immunity and vascular biology, with emerging diagnostic and therapeutic potential across multiple human diseases.

References

Greenlee MC, Sullivan SA, Bohlson SS. Detection and characterization of soluble CD93 released during inflammation. Inflamm Res. 2009;58(12):909–919.
Langenkamp E, Zhang L, Lugano R, et al. Elevated expression of the C-type lectin CD93 in the glioblastoma vasculature regulates cytoskeletal rearrangements that enhance vessel function and reduce host survival. Cancer Res. 2015;75(21):4504–4516.
Barbera S, Lugano R, Pedalina A, et al. The C-type lectin CD93 controls endothelial cell migration via activation of the Rho family of small GTPases. Matrix Biol. 2021 May;99:1-17.

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