|Detection of ROBO2 in NTera‑2 Human Cell Line by Flow Cytometry. NTera‑2 human testicular embryonic carcinoma cell line was stained with Mouse Anti-Human ROBO2 APC‑conjugated Monoclonal Antibody (Catalog # FAB3147A, filled histogram) or isotype control antibody (Catalog # IC002A, open histogram). View our protocol for Staining Membrane-associated Proteins.|
Human ROBO2 is a 175 kDa member of the ROBO family of guidance molecules (1-3). The term ROBO derives from round-about, a description of the circuitous pathway axons take in the absence of a functional ROBO gene (3, 4). Human ROBO2 is a type I transmembrane (TM) glycoprotein that is synthesized as a 1378 amino acid (aa) precursor. It contains a 21 aa signal sequence, an 838 aa extracellular domain (ECD), a 21 aa transmembrane segment, and a 498 aa cytoplasmic region (5, 6). The ECD contains five C2-type Ig-like domains (aa 31-504) and three fibronectin (FN) type III domains (aa 522-826). The cytoplasmic region contains multiple 15-20 aa long CC (Conserved Cytoplasmic) motifs (C0-C2) that are found in ROBO1 (7, 8). Human ROBO2 has at least two potential isoforms. One isoform shows a cytoplasmic truncation of the C-terminus (aa 1186-1378) (9). A second isoform is a 570 aa soluble form that shows a deletion of the first two and one-half C2-type Ig-like domains (aa 22-285) and terminates after the third fibronectin domain with a unique 20 aa sequence (10). Based on mouse and rat ROBO2 GenBank sequences, considerably more alternate splice forms may occur. Human ROBO2 ECD shares 98% aa sequence identity with the ECD in mouse and canine ROBO2. ROBO2 would appear to play a number of roles in cell adhesion. In the neural tube, it is the receptor for a chemorepulsant. Axons that cross the midline are directed, presumably by ROBO2/SLIT chemorepulsion, to lateral positions in the contralateral spinal cord (6, 11, 12). In addition, ROBO2 is both permissive for neurite outgrowth (via ROBO1-ROBO2 interaction) and inhibitory for neurite outgrowth (via ROBO2-SLIT interaction) (13, 14).