Disease relevance of TPK1

• Stability of neutral trehalase during heat stress in Saccharomyces cerevisiae is dependent on the activity of the catalytic subunits of cAMP-dependent protein kinase, Tpk1 and Tpk2 [1].

High impact information on TPK1

• We have isolated mutant TPK genes that suppress all of the bcy1- defects [2].
• We have isolated three genes (TPK1, TPK2, and TPK3) from the yeast S. cerevisiae that encode the catalytic subunits of the cAMP-dependent protein kinase [3].
• The TPK1 gene carried on a multicopy plasmid can suppress both a temperature-sensitive ras2 gene and adenylate cyclase gene [3].
• Comparison of the predicted amino acid sequences of the TPK genes indicates conserved and variable domains [3].
• Although they are redundant for viability, the three A kinases are not redundant for pseudohyphal growth [Robertson, L. S. & Fink, G. R. (1998) Proc. Natl. Acad. Sci. USA 95, 13783-13787; Pan, X. & Heitman, J. (1999) Mol. Cell. Biol. 19, 4874-4887]; Tpk2, but not Tpk1 or Tpk3, is required for pseudohyphal growth [4].

Biological context of TPK1

• Mutants lacking both TPK1 alleles showed defective hyphal morphogenesis on solid inducing media, whereas in liquid hypha, formation was affected slightly [5].
• We cloned SRA1 and SRA3 and determined their DNA sequences [6].
• Disruption of pka1 slows cell growth but is not lethal [7].
• Protein extracts from purified mitochondria from each of the three possible double TPK mutants show mt cAMP-dependent protein phosphorylation [8].
• The overactive PKA phenotype was abolished by mutations in the Tpk1 or Tpk2 catalytic subunits [9].

Anatomical context of TPK1

• Tpk1 is required for the derepression of branched chain amino acid biosynthesis genes that seem to have a second role in the maintenance of iron levels and DNA stability within mitochondria [4].
• In isolated vacuoles of yeast yvc1 disruption mutants, the TPK1 gene product shows ion channel activity with some characteristics very similar to the SV-type channel [10].

Associations of TPK1 with chemical compounds

• Yeast transformants containing increased kinase activity resulting from overexpression of RAS2Val19 or TPK1 and yeast strains having increased kinase activities due to mutations in the BCY1 gene also did not show alterations in their sensitivity to cisplatin [11].
• We have purified and characterized the catalytic subunit, C1, encoded by the TPK1 gene [12].
• In the bcy1 tpk2 mutant, protein kinase A activity (due to the presence of the TPK1 gene) was cyclic AMP independent, indicating that the cells harbored an unregulated phosphotransferase activity [13].
• SRA3 is homologous to protein kinases that phosphorylate serine and threonine and likely encodes the catalytic subunit of the cAMP-dependent protein kinase [6].
• In order to purify C1 completely free of C2 and C3, a strain was constructed that contained only the TPK1 gene and genetic disruptions of the other two TPK genes [12].

Physical interactions of TPK1

• Yeast pyruvate kinase Pyk1 identified by amino acid microsequencing analysis and immunoblotting with anti-Pyk1 antibodies copurified with the PKA-1 but not the -2 fraction [14].

Enzymatic interactions of TPK1

• The strain containing TPK3 as the only intact TPK gene showed nearly undetectable phosphorylating activity and no TPK3 mRNA could be detected, although the cells grow normally [15].
• Both glutathione S-transferase (GST)-Pyk1 and GST-Pyk2 were phosphorylated in vitro by the bovine heart protein kinase A (PKA) catalytic subunit and by immobilized yeast HA-Tpk1 [16].
• The results indicate that either rapamycin did not suppress the derepression of sexual development of strains in which adenylate cyclase was deleted or the cyclic AMP-dependent protein kinase encoded by pka1 was mutated [17].

Regulatory relationships of TPK1

• We find that purified Mck1p inhibits purified Tpk1p in vitro, in the presence or absence of Bcy1p [18].

Other interactions of TPK1

• TPK1 and TPK2 encode both isoforms of protein kinase A (PKA) catalytic subunits in Candida albicans [5].
• TPK1, which encodes a catalytic subunit of PKA, is a multicopy suppressor of the recombination and growth defects of sch9 mutants, suggesting that increased PKA activity compensates for SCH9 loss [19].
• Furthermore, a deficiency of the cAMP-binding regulatory subunit (RA) caused by the bcy1 mutation fails to suppress the cdc25 mutation, indicating that PK-25 does not interact with the cAMP receptor protein [20].
• The cdc25-suppressing protein kinase (PK-25) shows 48% sequence similarity to the catalytic subunit (CA) of mammalian cAMP-dependent protein kinase and 27-31% similarity to cyclic nucleotide-independent enzymes, including the yeast CDC28 gene product [20].
• Finally, and importantly, TOR controls the subcellular localization of both the protein kinase A catalytic subunit TPK1 and the RAS/cAMP signaling-related kinase YAK1 [21].

Analytical, diagnostic and therapeutic context of TPK1

• A truncated variant of TPK1, the yeast cAMP-dependent protein kinase catalytic subunit, was overexpressed in an engineered strain of Saccharomyces cerevisiae, purified by liquid chromatography, and crystallized from solutions of 2-propanol and magnesium at alkaline pH [22].
• Mutants lacking the serotype A protein kinase A (PKA) catalytic subunit Pka1 are unable to mate, fail to produce melanin or capsule, and are avirulent in animal models, whereas mutants lacking the PKA regulatory subunit Pkr1 overproduce capsule and are hypervirulent [23].

References