Welcome to Gaia! :: View User's Journal | Gaia Journals

Our previous results have demonstrated that Rac1 signaling leads to the activation of SSH proteins in migrating CEP18770 [8]. In contrast, inhibition of Rac1 signaling leads to an increase in 14-3-3/SSH interactions [8]. Several 14-3-3 isoforms, including β, γ, τ, and, ζ have been shown to bind SSH1 and inhibit its phosphatase activity [9]. However, the exact 14-3-3 isoforms that make up the homo- or heterodimers that bind SSH1 in keratinocytes have not been determined. Thus, to identify the specific 14-3-3 isoforms that bind SSH1 in skin cells, we immunoprecipitated V5 tagged SSH1 from keratinocytes treated with a Rac1 inhibitor and probed the precipitate with 14-3-3 isoform specific antibodies. Our results indicate that SSH1 interacts with endogenous 14-3-3ζ and τ isoforms upon Rac1 inhibition ( Fig. 1A).
Fig. 1.
Figure optionsDownload full-size imageDownload as PowerPoint slide
14-3-3ζ Heterodimerizes with 14-3-3τ in migrating keratinocytes
We next investigated whether 14-3-3ζ and τ isoforms form homo- or heterodimers when interacting with SSH1. Previous results using mutant 14-3-3 proteins in which either the carboxy-terminal or amino-terminal residues are removed, indicate that the amino-terminus of 14-3-3 is required for dimerization [23]. Thus, we used 14-3-3ζ amino- and carboxy-terminal deletion mutants, 14-3-3ζΔN and 14-3-3ζΔC consisting of either amino acid residues 140–245 or residues 1–139, respectively, as tools to determine whether homodimers of 14-3-3ζ or heterodimers of 14-3-3ζ/τ exist in keratinocytes. Specifically, 14-3-3ζΔC should form dimers whereas 14-3-3ζΔN should not.