The Dictyostelium prestalk inducer differentiation-inducing factor-1 (DIF-1) triggers unexpectedly complex global phosphorylation changes.
Bottom Line: The results also provide evidence that the Ca(2+)/calmodulin-dependent phosphatase calcineurin plays a role in DIF-1 signaling to the DimB prestalk transcription factor.This accords with studies that suggest an antagonism between the two inducers and also with the rapid dephosphorylation of the cAMP receptor that we observe in response to DIF-1 and with the known inhibitory effect of DIF-1 on chemotaxis to cAMP.All MS data are available via ProteomeXchange with identifier PXD001555.
Affiliation: College of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom.Show MeSH
Mentions: We identify class I phosphorylation sites on several proteins that have a direct involvement with Ca2+, and most show dephosphorylation in response to DIF-1 (Supplemental Figure S2). In addition, we observe transient phosphorylation upon four phosphorylation sites in an 18-residue stretch of CanA, the catalytic subunit of the protein phosphatase calcineurin (Figure 3A). Calcineurin is a Ca2+- and calmodulin (CaM)-dependent protein phosphatase that is well conserved from yeast to mammals and is critical to many cellular processes (Rusnak and Mertz, 2000). In its inactive form, calcineurin is a heterodimer of CanA and its regulatory subunit CanB. Increasing Ca2+ allows CaM to bind, displacing the autoinhibitory domain and forming an active calcineurin heterotrimer. In this way, cellular Ca2+ regulates calcineurin phosphatase activity. Ca2+-dependent binding of CaM to Dictyostelium CanA has been demonstrated and putative CaM-binding domains identified, but, unusually, Ca2+/CaM is not essential for Dictyostelium calcineurin activity, which can also be activated by long-chain fatty acids, including arachidonic acid (Kessen et al., 1999; Catalano and O'Day, 2008).
Affiliation: College of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom.