Medical Research

University of California, Riverside

Sachiko Haga-Yamanaka, Naoki Yamanaka, Frances Sladek
Riverside, CA
December 2017

Steroid hormones regulate diverse biological processes, including immune response, energy homeostasis, sexual maturation and cancer progression.  In contrast to the extensive knowledge on their biosynthesis and downstream signaling, relatively little is known about the mechanisms that regulate steroid transport across cell membranes.  This is due to the widely accepted notion that lipophilic steroid hormones can freely enter and exit cells by simple diffusion across lipid bilayers.  However, the simple diffusion model of steroid hormone transport has not been critically tested in any in vivo model to date.  Work by three investigators at the University of California, Riverside, challenges this dogma by showing that a membrane transporter (named ecdysone importer) is required for cellular uptake of ecdysone, the primary insect steroid hormone, in the fruit fly model system.  Importantly, the same type of transporters exists in a wide variety of animals as well as humans.  The team therefore hypothesizes that mammalian steroid hormones also need transporters to enter target tissues.  Successful completion of this project would overturn the long-standing paradigm in endocrinology that steroid hormones enter cells by simple diffusion.  Moreover, the transporters are ideal targets for drug development to control steroid hormone function in vivo.

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