Table 1.
Different isoforms of 14-3-3 and their physiological function
| Physico-chemical characteristics and functions | ||||
|---|---|---|---|---|
| Alternative name | Physico-chemical features | Functional characteristics | Changes in phenotype after knockdown | |
| Isoformsa | ||||
| β | α (Kjarland et al. 2006) | – | Phosphorylated by protein kinase C (van Heusden 2005) May have oncogenic properties (Niemantsverdriet et al. 2008) |
– |
| γ | – | – | An upstream regulator of p53, may serve as a tumor suppressor (Niemantsverdriet et al. 2008) | 14-3-3γ knock-out mice: survival not affected, although some protein level changed (van Heusden 2005) |
| ε | – | Only form heterodimer (Kjarland et al. 2006) | Related to neuronal migration (Kjarland et al. 2006) | – |
| ζ | δ (Kjarland et al. 2006) | After being phosphorylated on Ser58, dimer disrupted (Woodcock et al. 2003) | Related to cellular metabolism (Kjarland et al. 2006) Can bind phosphorylated PAR3 (Kjarland et al. 2006) Can be phosphorylated by Bcr, leading to change in activity (Aitken 2006) Cannot be phosphorylated by protein kinase C (van Heusden 2005) Likely to behave as an oncogene (Niemantsverdriet et al. 2008) |
14-3-3ζ knockdown in human epithelial cell line: sensitized stress- induced apoptosis and induced expression of adhesion proteins (Niemantsverdriet et al. 2008) Myc–14-3-3ζ overexpression disrupts polarity in MDCK cells, while it is associated with Par3 and aPKC (Hurd et al. 2003) |
| η | – | – | May serve as a tumor repressor (Niemantsverdriet et al. 2008) | – |
| θ | τ (Aitken 2006) | Present in male germ cells (Berruti 2000) Can be phosphorylated by Bcr (van Heusden 2005) and protein kinase C (Aitken 2006) Stimulates apoptosis (Niemantsverdriet et al. 2008) |
– | |
| σ | – | Only form homodimers (Bridges & Moorhead 2005, Kjarland et al. 2006); least conserved, derived from a retrotransposon event (Bridges & Moorhead 2005) | Related to cell-cycle regulation (Bridges & Moorhead 2005, Kjarland et al. 2006) Expression induced after DNA damage (van Heusden 2005) Highly expressed in epithelial cells (Aitken 2006) May serve as a tumor repressor (van Heusden 2005) |
– |
a
All members of the 14-3-3 family share similar Mr as of 30 kDa.