Identification of Ran-binding protein M as a stanniocalcin 2 interacting protein and implications for androgen receptor activity

Stanniocalcin (STC), a glycoprotein hormone originallydiscovered in fish, has been implicated in calcium andphosphate homeostasis. While fishes and mammals possesstwo STC homologs (STC1 and STC2), the physiological roles ofSTC2 are largely unknown compared with those of STC1. Inthis study, we identified Ran-binding protein M (RanBPM) as anovel binding partner of STC2 using yeast two-hybridscreening. The interaction between STC2 and RanBPM wasconfirmed in mammalian cells by immunoprecipitation. STC2enhanced the RanBPM-mediated transactivation of ligandedandrogen receptor (AR), but not thyroid receptor β,glucocorticoid receptor, or estrogen receptor β. We also foundthat AR interacted with RanBPM in both the absence andpresence of testosterone (T). Furthermore, we discovered thatSTC2 recruits RanBPM/AR complex in T-dependent manner. Taken together, our findings suggest that STC2 is a novelRanBPM-interacting protein that promotes AR transactivation.