NEO1 and cancer: In cancer cells, Neogenin is proteolytically processed by Υ-secretase upon binding of soluble full-length RGMa.15 To evaluate the involvement of Υ-secretase in RGMa-mediated axonal inhibition, we studied the expression pattern of Presenilin-1, a member of the Υ-secretase protein complex, and showed expression by RGCs (Figure 4a).