Haem-dependent dimerization of PGRMC1/Sigma-2 receptor facilitates cancer proliferation and chemoresistance.

Yoshio Kabe ,Takanori Nakane,Hiroshi Handa,Kazumi Muraoka,Kenji Sugase,Koichiro Ishimori,Yuki Yamaguchi,Yuki Sugiura,Takeshi Uchida,Elena Krayukhina,Ikko Koike,Tatsuro Shimamura,Susumu Uchiyama,Makoto Suematsu,Mitsuyo Ohmura,Takuya Kobayashi,So Iwata,Tatsuya Yamamoto,Masanori Noda,Emiko Harada ,Ai Yamamoto

doi:10.1038/ncomms11030

Abstract

Progesterone-receptor membrane component 1 (PGRMC1/Sigma-2 receptor) is a haem-containing protein that interacts with epidermal growth factor receptor (EGFR) and cytochromes P450 to regulate cancer proliferation and chemoresistance; its structural basis remains unknown. Here crystallographic analyses of the PGRMC1 cytosolic domain at 1.95 Å resolution reveal that it forms a stable dimer through stacking interactions of two protruding haem molecules. The haem iron is five-coordinated by Tyr113, and the open surface of the haem mediates dimerization. Carbon monoxide (CO) interferes with PGRMC1 dimerization by binding to the sixth coordination site of the haem. Haem-mediated PGRMC1 dimerization is required for interactions with EGFR and cytochromes P450, cancer proliferation and chemoresistance against anti-cancer drugs; these events are attenuated by either CO or haem deprivation in cancer cells. This study demonstrates protein dimerization via haem–haem stacking, which has not been seen in eukaryotes, and provides insights into its functional significance in cancer.

Highlights

Progesterone-receptor membrane component 1 (PGRMC1/Sigma-2 receptor) is a haem-containing protein that interacts with epidermal growth factor receptor (EGFR) and cytochromes P450 to regulate cancer proliferation and chemoresistance; its structural basis remains unknown
In cytochrome b5, the haem iron is six-coordinated by two axial histidine residues
These histidines are missing in progesterone-receptor membrane component 1 (PGRMC1), and the haem iron is five-coordinated by Tyr[113] (Y113) alone (Fig. 1b and Supplementary Fig. 3)

Summary

Results

CO application to ferrous PGRMC1 abolished the haem-dependent increase in its molecular size Under this reducing condition in the presence of dithionite, analyses of UV-visible spectra indicated that CO-binding with haem-PGRMC1 is stable, showing only 20% reduction of the absorbance at 412 nm within 2 h (Supplementary Fig. 14). Differences in molecular weights of the wild-type (wt; a) and the C129S mutant (b) PGRMC1 proteins in the absence (apo form) or the presence of haem (haem-bound form). The cytosolic domain of wild-type PGRMC1, but not the Y113F mutant, interacted with purified EGFR in a haem-dependent manner. EGFR signaling was suppressed by treatment of HCT116 cells with SA (Fig. 4g) or CORM3 (Fig. 4h) These results suggested that haem-mediated dimerization of PGRMC1 is critical for EGFR signaling.

21 Ferrous haem

Discussion

Methods