PMID: 23333428

Authors:

Johansson P, Bernstrom J, Gorman T, Oster L, Backstrom S, Schweikart F, Xu B, Xue Y, Schiavone LH

Title:

FAM3B PANDER and FAM3C ILEI Represent a Distinct Class of Signaling Molecules with a Non-Cytokine-like Fold.

Journal:

Structure. 2013 Jan 15. pii: S0969-2126(12)00464-9. doi:, 10.1016/j.str.2012.12.009.

Abstract:

The FAM3 superfamily is predicted to contain classical four-helix bundle cytokines, featuring a typical up-up-down-down fold. Two members of FAM3 have been extensively studied. FAM3B PANDER has been shown to regulate glucose homeostasis and beta cell function, whereas the homologous FAM3C ILEI has been shown to be involved in epithelial-mesenchymal transition and cancer. Here, we present a three-dimensional structure of a FAM3 protein, murine PANDER. Contrary to previous suggestions, PANDER exhibits a globular beta-beta-alpha fold. The structure is composed of two antiparallel beta sheets lined by three short helices packing to form a highly conserved water-filled cavity. The fold shares no relation to the predicted four-helix cytokines but is conserved throughout the FAM3 superfamily. The available biological data and the unexpected new fold indicate that FAM3 PANDER and ILEI could represent a new structural class of signaling molecules, with a different mode of action compared to the traditional four-helix bundle cytokines.