Multi-chaperone function modulation and association with cytoskeletal proteins are key features of the function of...

Area of Science:

• Endocrinology
• Molecular Biology
• Oncology

Background:

• Loss-of-function mutations in the aryl hydrocarbon receptor interacting protein (AIP) gene predispose individuals to pituitary adenomas.
• The precise pituitary-specific function of AIP as a tumor suppressor remains largely unknown.

Purpose of the Study:

• To identify interacting partners of the AIP protein in somatotroph cells.
• To elucidate the functional consequences of AIP mutations in pituitary tumor development.

Main Methods:

• Pull-down assays and quantitative mass spectrometry were employed to identify AIP interacting proteins using wild-type and variant AIP.
• Co-immunoprecipitation and co-localization validated novel interactions.
• RNA microarrays analyzed global gene expression in AIP mutation-positive and negative pituitary adenomas.

Main Results:

• Three known and six novel interacting partners of AIP were identified, including chaperones (HSPA5, HSPA9, HSP90AA1, HSP90AB1, HSPA8) and cytoskeletal proteins (TUBB, TUBB2A).
• Specific AIP variants (p.R304* and p.R304Q) demonstrated impaired interactions with several partners, including HSPA8, HSP90AB1, NME1, SOD1, TUBB, and TUBB2A.
• AIP-mutated tumors exhibited reduced TUBB2A expression.

Conclusions:

• AIP's tumor suppressor activity likely involves regulating chaperone client proteins, cytoskeletal organization, cell motility/adhesion, and oxidative stress responses.
• Deficient AIP function due to mutations may perturb these critical cellular processes, contributing to pituitary adenoma formation.