Protein kinase C phosphorylates pp60src at a novel site

Area of Science:

• Molecular Biology
• Cellular Signaling
• Oncology

Background:

• pp60v-src (Rous sarcoma virus transforming protein) and pp60c-src (cellular homolog) are key proteins in cell growth.
• Phosphorylation is a critical regulatory mechanism for protein function.

Purpose of the Study:

• To identify the kinase responsible for in vivo phosphorylation of pp60src at serine 12.
• To investigate the role of protein kinase C in pp60src modification.

Main Methods:

• In vivo phosphorylation studies using tumor promoters (12-O-tetradecanoylphorbol-13-acetate, teleocidin) and diacylglycerol.
• In vitro kinase assays with purified pp60c-src/pp60v-src and various serine/threonine-specific protein kinases.
• In vitro phosphorylation of a synthetic peptide mimicking pp60c-src N-terminus using purified protein kinase C.

Main Results:

• Tumor promoters and diacylglycerol induced significant pp60src phosphorylation at serine 12 in vivo.
• Only purified protein kinase C phosphorylated pp60c-src and pp60v-src at serine 12 in vitro.
• Purified protein kinase C phosphorylated a synthetic peptide at serine 12, confirming its activity site.

Conclusions:

• Protein kinase C is the primary kinase responsible for pp60src phosphorylation at serine 12 in vivo.
• This novel phosphorylation event by protein kinase C may have significant physiological implications.
• Further research is warranted to elucidate the functional consequences of serine 12 phosphorylation.