Anti-MEMO1 (aa 143-192) polyclonal antibody

ErbB2 signaling pathways are linked to breast cancer formation, growth, and aggression; therefore, understanding the behavior of proteins associated with these pathways as well as regulatory factors that influence ErbB2 function is essential. MEMO1 is a redox active protein that is shown to associate with phosphorylated ErbB2 and mediate cell motility. We have developed a fluorescence polarization assay to probe the interaction between MEMO1 and an ErbB2derived peptide containing a phosphorylated tyrosine residue. This interaction is shown to be pH-dependent and stronger with longer peptides as would be expected for protein protein interactions. We have quantitatively mapped the binding interface of MEMO1 to the peptide using the fluorescence polarization assay and molecular dynamics simulations. We have confirmed that phosphorylation of the peptide is essential for binding and through mutagenesis have identified residues that contribute to favorable interactions. Our results highlight the importance of the protein protein interactions of MEMO1 that complement the oxidase activity. In the future, these studies will provide a method for screening for selective modulators of MEMO1, which will allow for additional biological investigations.

Mediator of cell motility 1 (MEMO1) is a ubiquitously expressed modulator of cellular responses to growth factors including FGF23 signaling, and Memo1-deficient mice share some phenotypic traits with Fgf23- or Klotho-deficient mouse models. Here, we tested whether Memo1 gene expression is regulated by calciotropic hormones or by changing the dietary mineral load. MLO-Y4 osteocyte-like cells were cultured and treated with 1,25(OH)(2)-vitamin D-3. Wild-type C57BL/6N mice underwent treatments with 1,25(OH)(2)-vitamin D-3, parathyroid hormone, 17 beta-estradiol or vehicle. Other cohorts of C57BL/6N mice were fed diets varying in calcium or phosphate content. Expression of Memo1 and control genes was assessed by qPCR. 1,25(OH)(2)-vitamin D-3 caused an acute decrease in Memo1 transcript levels in vitro, but not in vivo. None of the hormones tested had an influence on Memo1 transcripts, whereas the assessed control genes reacted the expected way. Dietary interventions with calcium and phosphate did not affect Memo1 transcripts but altered the chosen control genes' expression. We observed that Memo1 was not regulated by calciotropic hormones or change in mineral load, suggesting major differences between the regulation and physiological roles of Klotho, Fgf23, and Memo1.