Transcriptional regulation of HIF1α-mediated STAR expression in murine KK1 granulosa cell line involves cJUN, CREB and CBP-dependent pathways

Bettina Lanfranchi; Ricardo Fernandez Rubia; Max Gassmann; Gerhard Schuler; Mariusz P Kowalewski

doi:10.1016/j.ygcen.2021.113923

Transcriptional regulation of HIF1α-mediated STAR expression in murine KK1 granulosa cell line involves cJUN, CREB and CBP-dependent pathways

Gen Comp Endocrinol. 2022 Jan 1:315:113923. doi: 10.1016/j.ygcen.2021.113923. Epub 2021 Oct 2.

Authors

Bettina Lanfranchi¹, Ricardo Fernandez Rubia², Max Gassmann³, Gerhard Schuler⁴, Mariusz P Kowalewski⁵

Affiliations

¹ Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich (UZH), Zurich, Switzerland.
² Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich (UZH), Zurich, Switzerland. Electronic address: ricardo.fernandezrubia@uzh.ch.
³ Institute of Veterinary Physiology, Vetsuisse Faculty and Zurich Center for Integrative Human Physiology, University of Zurich, Zurich, Switzerland. Electronic address: maxg@access.uzh.ch.
⁴ Clinic for Obstetrics, Gynecology and Andrology of Large and Small Animals, Justus-Liebig-University, Giessen, Germany. Electronic address: Gerhard.Schuler@vetmed.uni-giessen.de.
⁵ Institute of Veterinary Anatomy, Vetsuisse Faculty, University of Zurich (UZH), Zurich, Switzerland. Electronic address: kowalewski@vetanat.uzh.ch.

PMID: 34606743
DOI: 10.1016/j.ygcen.2021.113923

Abstract

Gonadal function is connected to hypoxia, with hypoxia-inducible factor (HIF) 1α, as a component of HIF1-complexes, regulating cellular adaptation to hypoxic conditions. In the ovary, it regulates follicular maturation, ovulation and luteal development. At the cellular level, HIF1-complexes coordinate the expression of steroidogenic acute regulatory protein (STAR), and thereby ovarian steroidogenesis. The functionality of STAR is associated with the cAMP/PKA-dependent pathways. In vitro, HIF1α is required for basal and cAMP-induced STAR expression, under ambient and reduced oxygen (O₂) tension. Lowering O₂ increases the responsiveness of the Star promoter towards cAMP and PKA mediates activation/phosphorylation (P) of several transcriptional factors, including cJUN and cAMP response element-binding protein (CREB), whose functionality is linked to HIF1 through utilization of CREB-binding protein (CBP). Since the mechanisms underlying HIF1α-dependent expression of STAR remain unknown, we investigated the involvement of HIF1α in CREB-, cJUN- and CBP-mediated expression of STAR using a well-characterized steroidogenic model, murine KK1 granulosa cells; ambient and lowered (10%) O₂ were applied. Our main findings were that while functional suppression of the α-subunit of HIF1 lowered STAR/P-STAR and steroidogenic output from granulosa cells, surprisingly the levels of P-CREB and its transcriptional activity were strongly induced. However, its association with the Star promoter was decreased, indicating dissociation of P-CREB from the promoter. Further, suppression of HIF1 activity ultimately diminished the expression of cJUN/P-cJUN and CBP. Finally, the study suggests that HIF1-complex: (1) regulates cJUN expression in granulosa cells, (2) is involved in regulating the recruitment of P-CREB to the Star promoter in (3) a mechanism which possibly involves the HIF1-dependent regulation of CBP expression.

Keywords: CREB; Granulosa cells; HIF1α; STAR; Transcriptional regulation; cJUN.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
CREB-Binding Protein / metabolism
Cyclic AMP Response Element-Binding Protein* / genetics
Cyclic AMP Response Element-Binding Protein* / metabolism
Female
Gene Expression Regulation
Granulosa Cells* / metabolism
Hypoxia-Inducible Factor 1, alpha Subunit* / metabolism
Metabolic Networks and Pathways
Mice
Phosphoproteins* / genetics
Proto-Oncogene Proteins c-jun / metabolism

Substances

Creb1 protein, mouse
Cyclic AMP Response Element-Binding Protein
Hif1a protein, mouse
Hypoxia-Inducible Factor 1, alpha Subunit
Phosphoproteins
Proto-Oncogene Proteins c-jun
steroidogenic acute regulatory protein
CREB-Binding Protein
Crebbp protein, mouse