Phosphorylation of protein phosphatase 2Czeta by c-Jun NH2-terminal kinase at Ser92 attenuates its phosphatase...

Area of Science:

• Cellular Biology
• Biochemistry
• Molecular Biology

Background:

• Protein phosphatase 2C (PP2C) is a major family of protein Ser/Thr phosphatases in mammalian cells.
• PP2C family members regulate diverse cellular functions, but their regulatory mechanisms remain largely unknown.
• PP2Czeta is a PP2C family member specifically enriched in testicular germ cells.

Purpose of the Study:

• To investigate the regulation of PP2Czeta activity.
• To identify kinases that phosphorylate PP2Czeta.
• To determine the functional consequences of PP2Czeta phosphorylation.

Main Methods:

• In vitro kinase assays using c-Jun NH 2-terminal kinase (JNK) and p38.
• Mass spectrometry and mutational analyses to identify phosphorylation sites.
• Ectopic expression of PP2Czeta in 293 cells under various stress conditions.
• Inhibition studies using JNK, p38, and MEK inhibitors.
• Assessment of PP2Czeta phosphatase activity in cells.

Main Results:

• PP2Czeta is phosphorylated by JNK, but not by p38, in vitro.
• Phosphorylation occurs at Ser92, Thr202, and Thr205.
• Osmotic stress enhances PP2Czeta phosphorylation, which is mediated by JNK.
• JNK-mediated phosphorylation of PP2Czeta represses its phosphatase activity.
• Mutation of Ser92 to alanine suppresses JNK-induced inhibition of PP2Czeta activity.

Conclusions:

• Stress-activated JNK specifically phosphorylates PP2Czeta at Ser92.
• Phosphorylation of PP2Czeta at Ser92 by JNK attenuates its phosphatase activity.
• This finding reveals a novel regulatory mechanism for PP2Czeta in response to cellular stress.