Caveolin-Na/K-ATPase interactions: Role of transmembrane topology in non-genomic steroid signal transduction

► Progesterone binds to transmembrane helix of Na/K-ATPase and adjacent external loop. ► Progesterone-activated steroid and lipid enzymes contain caveolin binding motifs. ► Caveolin exhibits helix-turn-helix topology with Na/K-ATPase binding domains. ► Steroid activation of PE-NMT shifts Na/K-ATPase to caveolar membrane region. ► Na/K-ATPase-caveolin-steroid reductase-signal complex triggers meiotic divisions.