The Steroid Hormone 20-Hydroxyecdysone Enhances Gene Transcription through the cAMP Response Element-binding Protein (CREB) Signaling Pathway

Yu-Pu Jing,Di Wang,Xiao-Lin Han,Du-Juan Dong,Jin-Xing Wang,Xiao-Fan Zhao

doi:10.1074/jbc.m115.706028

Abstract

Animal steroid hormones regulate gene transcription through genomic pathways by binding to nuclear receptors. These steroid hormones also rapidly increase intracellular calcium and cyclic adenosine monophosphate (cAMP) levels and activate the protein kinase C (PKC) and protein kinase A (PKA) nongenomic pathways. However, the function and mechanism of the nongenomic pathways of the steroid hormones are unclear, and the relationship between the PKC and PKA pathways is also unclear. We propose that the steroid hormone 20-hydroxyecdysone (20E) activates the PKA pathway to enhance 20E-induced gene transcription in the lepidopteran insect Helicoverpa armigera The expression of the catalytic subunit 1 of PKA (PKAC1) increased during metamorphosis, and PKAC1 knockdown blocked pupation and repressed 20E-responsive gene expression. 20E regulated PKAC1 phosphorylation at threonine 200 and nuclear translocation through an ecdysone-responsive G-protein-coupled receptor 2. PKAC1 induced cAMP response element-binding protein (CREB) phosphorylation at serine 143, which bound to the cAMP response element on DNA to enhance 20E-responsive gene transcription. Through ecdysone-responsive G-protein-coupled receptor 2, 20E increased cAMP levels, which induced CREB PKA phosphorylation and 20E-responsive gene expression. This study demonstrates that the PKA/CREB pathway tightly and critically regulates 20E-induced gene transcription as well as its relationship with the 20E-induced PKC pathway.

Highlights

Steroid hormones, such as brassinosteroids in plants [1]; 20-hydroxyecdysone (20E)2 in insects [2]; and glucocorticoids [3], mineralocorticoids [4], androgens [5], estrogens [6], progestogens, and vitamin D [7] in mammals, regulate various biological processes, including growth and development, inflammation, immunity, and the salt and water balance
The nongenomic G-protein-coupled receptors (GPCRs), G␣q, phospholipase C (PLC) ␥1, calcium, and protein kinase C (PKC) signaling cascade has been identified in H. armigera, suggesting that the activation of the PKC pathway is necessary for USP phosphorylation and 20E-responsive gene transcription in the 20E genomic pathway [25, 26]. 20E triggered the lysine acetylation of USP1 by activating the digoxigenin; CC, chelerythrine chloride; dbcAMP, N6,2Ј-O-dibutyryladenosine 3Ј,5Ј-cyclic monophosphate sodium salt; EPAC, exchange protein directly activated by cyclic adenosine monophosphate (cAMP)
These results indicate that PKAC1 expression is similar to Helicoverpa armigera HR3 (HHR3) transcription during the larval developmental stages, suggesting a connection between PKAC1 expression and HHR3 transcription during the larval-pupal transition

Summary

Introduction

Steroid hormones, such as brassinosteroids in plants [1]; 20-hydroxyecdysone (20E) in insects [2]; and glucocorticoids [3], mineralocorticoids [4], androgens [5], estrogens [6], progestogens, and vitamin D [7] in mammals, regulate various biological processes, including growth and development, inflammation, immunity, and the salt and water balance Because of their lipid-soluble characteristics, steroid hormones are able to fuse with the cell membrane and regulate gene transcription through a genomic pathway based on nuclear receptors [8, 9]. An EcRE is found in the 5Ј upstream region of Helicoverpa armigera HR3 (HHR3; GenBankTM accession number AF337637), which can be activated by the binding of the EcRB1-USP1 complex associated with eat shock protein 90 and cyclin-dependent protein kinase 10 [20, 21] These data suggest that the cAMP/PKA pathway is involved in 20E signaling

Results

Discussion

Conclusion