Calcium-dependent Nr4a1 expression in mouse Leydig cells requires distinct AP1/CRE and MEF2 elements

Area of Science:

• Endocrinology
• Molecular Biology
• Cell Signaling

Background:

• Nuclear receptor NR4A1 is crucial for steroidogenesis and male sex differentiation in Leydig cells.
• LH stimulation activates cAMP and Ca2+ pathways, inducing Nr4a1 expression, but downstream factors remain unclear.

Purpose of the Study:

• To identify downstream transcription factors mediating hormone-induced Nr4a1 expression via the Ca2+ pathway in MA-10 Leydig cells.

Main Methods:

• MA-10 Leydig cells treated with forskolin, dantrolene, and W7 to modulate cAMP and Ca2+ signaling.
• Analysis of Nr4a1 promoter regions for Ca2+-responsive elements and transcription factor binding sites (AP1, CREB, MEF2).
• Assessed recruitment of phospho-CREB and p300; utilized siRNA for CREB knockdown.

Main Results:

• Identified Ca2+-responsive elements in the Nr4a1 promoter, particularly AP1/CRE sites (-255 bp) and MEF2 sites (-315, -285 bp).
• Ca2+ pathway is essential for hormone-induced recruitment of phospho-CREB and p300 to the Nr4a1 promoter.
• CREB knockdown significantly impaired NR4A1 expression and steroidogenesis.

Conclusions:

• The Ca2+ signaling pathway upregulates Nr4a1 expression in Leydig cells, partly by enhancing coactivator recruitment via MEF2, AP1, and CREB.
• Demonstrates a significant interplay between Ca2+ and cAMP pathways in regulating Nr4a1 expression.
• Highlights the role of CREB in mediating Nr4a1's function in steroidogenesis.