The intrinsically disordered E-domains regulate the IGF-1 prohormones stability, subcellular localisation and...

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• Insulin-like growth factor-1 (IGF-1) is produced from a prohormone (proIGF-1).
• Alternative splicing of IGF-1 mRNA generates three proIGF-1 variants (proIGF-1Ea, proIGF-1Eb, proIGF-1Ec) with distinct E-domains.
• The structure and function of these E-domains remain largely uncharacterized.

Purpose of the Study:

• To investigate the structural and functional roles of proIGF-1 E-domains in IGF-1 production and regulation.
• To elucidate the impact of post-translational modifications, specifically N-glycosylation, on proIGF-1 variants.
• To determine how E-domains influence the subcellular localization of proIGF-1.

Main Methods:

• Analysis of intrinsically disordered regions (IDRs) within proIGF-1 E-domains.
• Investigation of N-glycosylation site in the Ea-domain using inhibitors like tunicamycin and glucose starvation.
• Treatment with 2-deoxyglucose to assess effects on proIGF-1Ea and mature IGF-1.
• Assessment of proIGF-1Eb and proIGF-1Ec production and localization in response to N-glycosylation modulation.
• Microscopy techniques to determine subcellular localization of proIGF-1 variants.

Main Results:

• E-domains are intrinsically disordered regions with distinct regulatory functions.
• A conserved N-glycosylation site in the Ea-domain regulates proIGF-1Ea stability and prevents proteasomal degradation.
• Inhibition of N-glycosylation reduces proIGF-1Ea and mature IGF-1 production, while 2-deoxyglucose increases them.
• ProIGF-1Eb and proIGF-1Ec lack N-glycosylation sites and are unaffected by inhibitors.
• Eb and Ec domains direct proIGF-1Eb and proIGF-1Ec to the nucleus, influencing their subcellular localization.

Conclusions:

• ProIGF-1 E-domains are crucial regulatory elements controlling IGF-1 production, secretion, and localization.
• N-glycosylation of the Ea-domain is a key mechanism for regulating proIGF-1Ea levels.
• Alternative E-domains dictate the subcellular trafficking of proIGF-1 variants, impacting their biological activity.