CLEC1B

CLEC1B Full Name

C-type lectin domain family 1, member B

CLEC1B Introduction

C-type lectin domain family 1 member B (CLEC1B), also known as CLEC-2, is a type II transmembrane glycoprotein that functions as a C-type lectin-like receptor primarily expressed on platelets, megakaryocytes, and liver sinusoidal endothelial cells. Unlike classical C-type lectins, CLEC1B lacks the canonical carbohydrate recognition domain residues required for calcium-dependent sugar binding, instead recognizing its endogenous ligand podoplanin, a sialomucin-like transmembrane glycoprotein. The CLEC1B-podoplanin interaction constitutes a critical signaling axis in multiple physiological and pathological processes, including lymphatic vessel development, thrombus formation, and tumor metastasis.

Figure 1. Strcuture of Protein CLEC1B.

Signaling Mechanism and Platelet Activation
CLEC1B signals through a conserved hemITAM (hemi-immunoreceptor tyrosine-based activation motif) sequence in its cytoplasmic tail. Upon podoplanin engagement, CLEC1B clustering promotes phosphorylation of the hemITAM by Src-family kinases (predominantly Syk), initiating a downstream signaling cascade involving Syk, PLCγ2, and SLP-76 adaptor proteins. This cascade culminates in platelet activation, shape change, granule secretion, and aggregation. Notably, CLEC1B-mediated signaling is distinct from that of the major platelet collagen receptor GPVI, despite utilizing overlapping downstream effectors. The CLEC1B pathway is also negatively regulated by the tandem SH2 domain-containing phosphatase SHIP-1, providing a mechanism for fine-tuning platelet responses to prevent unwarranted thrombosis.

Clinical Implications and Therapeutic Targeting
The CLEC1B-podoplanin axis has emerged as a significant player in cancer biology, as podoplanin is frequently upregulated on the surface of tumor cells and cancer-associated fibroblasts in a variety of malignancies including squamous cell carcinoma, mesothelioma, and glioblastoma. Podoplanin-induced platelet aggregation via CLEC1B facilitates tumor cell evasion of immune surveillance by forming a platelet shield around circulating tumor cells, promoting hematogenous metastasis. Pharmacological blockade of CLEC1B, for instance using monoclonal antibodies or small-molecule inhibitors, represents a promising anti-metastatic strategy. In addition, CLEC1B deficiency has been linked to impaired lymph-blood separation during development, underscoring its essential role in the establishment of functional lymphatic vasculature.

Alternate Names for CLEC1B

CLEC1B; C-type lectin domain family 1, member B; C-type lectin domain family 1 member B; CLEC2; CLEC-2; C-type lectin-like receptor 2; C-type lectin-like receptor-2; CLEC2B; PRO1384; QDED721; 1810061I13Rik;