Mouse C4.4A/LYPD3 Alexa Fluor™ Plus 680-conjugated Antibody

C4.4A, also known as Ly6/PLAUR domain containing 3 (LYPD-3), is a GPI-linked protein with structural similarity to the urokinase-type plasminogen activator receptor (uPAR) (1). Mature mouse C4.4A contains two uPAR/Ly6 domains and a Ser/Thr/Pro-rich (STP) region that includes a protease sensitive site (2, 3). Mouse C4.4A shares 80% and 92% amino acid sequence identity with human and rat C4.4A, respectively. It is a 65-100 kDa molecule with cell type-specific N- and O-linked glycosylation (4, 5). Proteolytic cleavage following the second uPAR/Ly6 domain generates a 35-40 kDa soluble form, while ADAM10 or ADAM17-mediated cleavage within the STP region generates a 90 kDa soluble form (6-8). Soluble C4.4A can also be shed and released in membrane vesicles (5). C4.4A is expressed in the suprabasal layers of stratified squamous epithelium and is upregulated on migrating keratinocytes during wound healing (6, 7). Its expression is downregulated during the onset of epithelial dysplasia but subsequently upregulated at the invasive front of melanomas and various carcinomas (2, 6, 5, 9). Metastases derived from these tumors also express high levels of C4.4A (2, 5, 6). The interaction of C4.4A with Laminin-1 and -5 on neighboring cells promotes the adhesion, spreading, and migration of tumor cells (4, 6, 10). C4.4A additionally interacts with Galectin-3 and the anterior gradient proteins AG-2 and AG-3 (10, 11). C4.4A over-expression in non-small cell lung cancer is predictive of increased mortality (12).