Mouse ASGR1/ASGPR1 Alexa Fluor™ Plus 594‑conjugated Antibody

The mouse asialoglycoprotein receptor (ASGP-R) is an endocytic recycling receptor that belongs to the long-form subfamily of the C-type/Ca⁺⁺-dependent lectin family (1‑3). It is a complex of two non‑covalently linked subunits, a major 42 kDa glycoprotein (ASGPR1), and a minor 51 kDa glycoprotein (ASGR2). The major mouse ASGP‑R subunit, ASGPR1, is synthesized as a 284 amino acid (aa) type II transmembrane (TM) protein that contains a 39 aa cytoplasmic region, a 21 aa TM segment, and a 224 aa extracellular domain (ECD) (4-6). The ECD contains two important structural regions. The first is a stalk region of 56 aa (aa’s 59-117) that contributes to non-covalent oligomerization. The second is a 118 aa, carbohydrate-binding, Ca⁺⁺-dependent C-type lectin domain (aa’s 160-277) that is unusually stabilized by three Ca⁺⁺ ions (3, 5). There are two potential alternate splice forms for ASGPR1. Both are TM and show a deletion of the C-type lectin domain. One is 113 aa in length and shows a deletion of aa’s 114-284 (7). The second is 132 aa in length and shows a deletion of aa’s 118-146 and aa’s 162-284 (8). Mouse ASGPR1 ECD is 89% and 79% aa identical to the ASGPR1 ECD in rat and human, respectively. The minor mouse ASGP-R subunit, ASGR2, is also a C-type lectin that shares the same structural organization as ASGR-1. It is 301 aa in length and has two 45 kDa and 51 kDa differentially-glycosylated isoforms (4, 6, 9). The ECD of ASGR2 is 50% aa identical to the ECD of ASGPR1. Although ASGPR1 and 2 can be expressed individually, a fully functional and stable ASGP-R requires simultaneous expression of both subunits (10-12). The stoichiometry of a functional ASGP-R is suggested to be either a 2:2, 3:1 or 3:2 ratio of ASGPR1:ASGR2 (13, 14). ASGPR1 is reported to bind Gal (nonreducing), GalNAc, and sialic acid alpha 2,6GalNAc (3, 15, 16). This is generally in the context of triantennary or tetraantennary configurations (2).