Calcium-Prolactin Secretion Coupling in Rat Pituitary Lactotrophs Is Controlled by PI4-Kinase Alpha

Area of Science:

• Endocrinology
• Cell Biology
• Molecular Signaling

Background:

• Calcium ions are essential for pituitary hormone release via exocytosis.
• The specific role of phosphatidylinositol kinases (PIKs) in calcium-driven prolactin (PRL) release remains to be fully elucidated.

Purpose of the Study:

• To investigate the contribution of PI4Ks, PIP5Ks, and PI3KCs to calcium-driven PRL release in rat pituitary lactotrophs.
• To determine the precise role of specific PIKs in the calcium-secretion coupling mechanism.

Main Methods:

• Single-cell RNA sequencing and qRT-PCR for gene expression analysis.
• Radioimmunoassay and ELISA for hormone level assessment.
• Fura 2 imaging for single-cell calcium signaling.
• Pharmacological inhibition using PIK-specific inhibitors (Wortmannin, LY294002, GSK-A1, PIK93, ISA2011B, UNC3230).

Main Results:

• Lactotrophs express various PIKs, including Pi4ka, Pip5k1a, Pip5k1c, and Pik3ca.
• Wortmannin inhibited PRL release and accumulation of intracellular PRL, but not calcium signaling.
• GSK-A1, a PI4KA inhibitor, blocked calcium-driven PRL secretion without affecting calcium signaling or PRL expression.
• Specific inhibitors of PI4KB, PIP5K1A, and PIP5K1C did not impact PRL release.

Conclusions:

• PI4KA is critical for calcium-secretion coupling in pituitary lactotrophs.
• PI4KA acts downstream of calcium signaling and PI(4,5)P2-dependent processes.
• This finding highlights a novel regulatory mechanism in hormone release.