Avian corticosteroid-binding globulin: biological function and regulatory mechanisms in physiological stress responses

Frontiers in Zoology - Tập 18 - Trang 1-11 - 2021
Hai-Yan Lin1, Gang Song1, Fumin Lei1, Dongming Li2, Yanhua Qu1
1Key Laboratory of Zoological Systematics and Evolution, Institute of Zoology, Chinese Academy of Sciences, Beijing, China
2Key Laboratory of Animal Physiology, Biochemistry and Molecular Biology of Hebei Province, College of Life Sciences, Hebei Normal University, Shijiazhuang, China

Tóm tắt

Corticosteroid-binding globulin (CBG) is a high-affinity plasma protein that binds glucocorticoids (GCs) and regulates their biological activities. The structural and functional properties of CBG are crucial to understanding the biological actions of GCs in mediating stress responses and the underlying mechanisms. In response to stress, avian CBGs modulate the free and bound fractions of plasma corticosterone (CORT, the main GC), enabling them to mediate the physiological and behavioral responses that are fundamental for balancing the trade-off of energetic investment in reproduction, immunity, growth, metabolism and survival, including adaptations to extreme high-elevation or high-latitude environments. Unlike other vertebrates, avian CBGs substitute for sex hormone-binding globulin (SHBG) in transporting androgens and regulating their bioavailability, since birds lack an Shbg gene. The three-dimensional structures of avian and mammalian CBGs are highly conserved, but the steroid-binding site topographies and their modes of binding steroids differ. Given that CBG serves as the primary transporter of both GCs and reproductive hormones in birds, we aim to review the biological properties of avian CBGs in the context of steroid hormone transportation, stress responses and adaptation to harsh environments, and to provide insight into evolutionary adaptations in CBG functions occurred to accommodate physiological and endocrine changes in birds compared with mammals.

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