A conserved docking site modulates substrate affinity for calcineurin, signaling output, and in vivo function.
Calcineurin, the conserved Ca(2+)/calmodulin-regulated protein phosphatase, mediates diverse aspects of Ca(2+)-dependent signaling. We show that substrates bind calcineurin with varying strengths and examine the impact of this affinity on signaling. We altered the calcineurin-docking site, or PxIxIT motif, in Crz1, the calcineurin-regulated transcription factor in S. cerevisiae, to decrease (Crz1(PVIAVN)) or increase (Crz1(PVIVIT)) its affinity for calcineurin. As a result, the Ca(2+)-dependent dephosphorylation and activation of Crz1(PVIAVN) are decreased, whereas Crz1(PVIVIT) is constitutively dephosphorylated and hyperactive. Surprisingly, the physiological consequences of altering calcineurin-Crz1 affinity depend on the growth conditions. Crz1(PVIVIT) improves yeast growth under several environmental stress conditions but causes a growth defect during alkaline stress, most likely by titrating calcineurin away from other substrates or regulators. Thus, calcineurin-substrate affinity determines the Ca(2+) concentration dependence and output of signaling in vivo as well as the balance between different branches of calcineurin signaling in an overall biological response.
Roy
Jagoree
J
Department of Biological Sciences, Stanford University, 371 Serra Mall, Stanford, CA 94305, USA.
Li
Huiming
H
Hogan
Patrick G
PG
Cyert
Martha S
MS
D001665:Binding Sites; D019703:Calcineurin / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017124:Conserved Sequence; D004268:DNA-Binding Proteins; D007700:Kinetics; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D013379:Substrate Specificity; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism; D014157:Transcription Factors; D016335:Zinc Fingers
C109868:CRZ1 protein, S cerevisiae; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D019703:Calcineurin