Differential localization of ErbB2 in different tissues of the rat female reproductive tract: Implications for the use of specific antibodies for ErbB2 analysis

ErbB2 has been implicated in numerous functions, including normal and aberr ant development of a variety of tissues. Although no soluble ligand has bee n identified for ErbB2, we have recently shown that ASGP-2, the transmembra ne subunit of the cell surface glycoprotein Muc4 (also called sialomucin co mplex, SMC), can act as an intramembrane ligand for ErbB2 and modulate its activity. Muc4/SMC is abundantly expressed at the apical surface of most ep ithelia of the rat female reproductive tract. Since Muc4/SMC can interact w ith, ErbB2 when they are expressed in the same cell and membrane, we invest igated whether these two proteins are co-expressed and co-localized in tiss ues of the female reproductive tract. Using an anti-ErbB2 antibody from Dak o, we found moderate staining at the basolateral surface of the oviduct and also around the cell membrane of the most superficial and medial layers of the stratified epithelia of the vagina. In contrast, Neomarkers neu Ab1 an tibody intensely stained the apical surface of the epithelium of the oviduc t and the medial and basal layers of the stratified epithelia of the vagina , substantially overlapping the distribution of Muc4/SMC. Furthermore, Muc4 /SMC and ErbB2 association in different tissues of the female reproductive tract was demonstrated by co-immunoprecipitation analysis. Interestingly, p hosphorylated ErbB2 detected by anti-phospho-ErbB2 is primarily present at the apical surface of the oviduct. Thus, our results show that differential ly localized forms of ErbB2 are recognized by different antibodies and rais e interesting questions about the nature of the different forms of ErbB2, t he mechanism for differential localization, and possible functions of ErbB2 in the female reproductive tract. They also raise a cautionary note about the use of different ErbB2 antibodies for expression and localization studi es. (C) 2001 Wiley-Liss, Inc.