Sphingolipids activate the endoplasmic reticulum stress surveillance pathway

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Proper inheritance of functional organelles is crucial for cell survival.
• The endoplasmic reticulum (ER) stress surveillance (ERSU) pathway in yeast ensures daughter cells receive a functional ER.

Purpose of the Study:

• To investigate the role of phytosphingosine (PHS) in activating the ER stress surveillance (ERSU) pathway.
• To elucidate the mechanism by which PHS influences ER stress response and organelle inheritance.

Main Methods:

• Utilizing myriocin to reduce PHS levels and observing ERSU phenotypes.
• Treating cells with Aureobasidin A to block sphingolipid synthesis.
• Analyzing ERSU response in yeast mutants with altered PHS levels (orm1Δorm2Δ).
• Performing lipid analyses to quantify PHS levels in ER-stressed cells.
• Assessing ERSU phenotypes upon addition of exogenous PHS.

Main Results:

• Reducing PHS levels impairs ERSU pathway induction.
• Inhibition of complex sphingolipid synthesis induces ERSU.
• Elevated PHS levels in orm1Δorm2Δ cells activate ERSU independently of ER stress.
• ER stress demonstrably increases PHS levels.
• Exogenous PHS effectively induces ERSU phenotypes.

Conclusions:

• Phytosphingosine (PHS) acts as a direct activator of the ER stress surveillance (ERSU) pathway.
• ER stress leads to elevated PHS levels, which then activate ERSU.
• The PHS-mediated ERSU activation ensures the inheritance of a functional ER, promoting daughter cell viability.