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Updated: Oct 1, 2026

Modified Yeast-Two-Hybrid System to Identify Proteins Interacting with the Growth Factor Progranulin
Published on: January 17, 2012
p21-activated protein kinase gamma-PAK in pituitary secretory granules phosphorylates prolactin
Polygena T Tuazon1, Mary Y Lorenson, Ameae M Walker
1Department of Biochemistry, University of California at Riverside, 92521, USA.
Abstract:
p21-activated protein kinase gamma-PAK phosphorylates prolactin (PRL) in rat pituitary secretory granules on Ser-177 and on the equivalent site, Ser-179, in recombinant human PRL. This is shown by comparison of phosphopeptide maps with the human PRL mutant S179D. gamma-PAK is present in rat and bovine granules as identified by in-gel phosphorylation of histone H4, and by immunoblotting. Thus, phosphorylation of PRL by gamma-PAK in granules produces the PRL molecule that has been shown to antagonize the growth-promoting activity of unmodified PRL, and is consistent with the identified role of gamma-PAK in the induction and maintenance of cytostasis.
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