cAMP-dependent protein kinase involves calcium tolerance through the regulation of Prz1 in Schizosaccharomyces pombe

The cAMP-dependent protein kinase Pka1 is known as a regulator of glycogenesis, meiosis, and stress responses in Schizosaccharomyces pombe. We demonstrated that Pka1 is responsible for calcium tolerance. Loss of functional components of the PKA pathway such as Git3, Gpa2, Cyr1, and Pka1 yields a CaCl₂-sensitive phenotype, while loss of Cgs1, a regulatory subunit of PKA, results in CaCl₂ tolerance. Cytoplasmic distribution of Cgs1 and Pka1 is increased by the addition of CaCl₂, suggesting that CaCl₂ induces dissociation of Cgs1 and Pka1. The expression of Prz1, a transcriptional regulator in calcium homeostasis, is elevated in a pka1∆ strain and in a wild type strain under glucose-limited conditions. Accordingly, higher expression of Prz1 in the wild type strain results in a CaCl₂-sensitive phenotype. These findings suggest that Pka1 is essential for tolerance to exogenous CaCl₂, probably because the expression level of Prz1 needs to be properly regulated by Pka1.