Cell migration

YSK1 is activated by the Golgi matrix protein GM130 and plays a role in cell migration through its substrate 14-3-3ζ. Preisinger, C. et al. J. Cell Biol. 164, 1009–1020 (2004)

How the Golgi apparatus alters its position in response to extracellular signalling has been unclear. But Preisinger et al. have found that the STE20 kinases YSK1 and MST4 interact with the Golgi matrix protein GM130. This induces autophosphorylation of a conserved residue, which, when mutated in YSK1 to alanine, impairs Golgi-apparatus localization, and cell migration and invasion. The adaptor protein 14-3-3ζ, a Golgi-localized target of YSK1, might link YST1 signalling with migratory responses.

Development

FGF8-like1 and FGF8-like2 encode putative ligands of the FGF receptor Htl and are required for mesoderm migration in the Drosophila gastrula. Gryzik, T. & Müller, H. -A. J. Curr. Biol. 1 April 2004 (doi:10.1016/S0960982204002362)

In early Drosophila gastrulation, the fibroblast growth factor (FGF) receptor Heartless (Htl) is needed for mesoderm cells to migrate the ligand of Htl until now has been unknown. Gryzik and Müller have now identified two genes that encode FGF homologues. Ectodermally expressed FGF8-like1 and FGF8-like2 are required for Htl-expressing mesodermal cells to undergo the cell-shape changes that are required for migration by activating the mitogen-activated-protein-kinase pathway in these cells.

Ubiquitylation

A novel protein-conjugating system for Ufm1, a ubiquitin-fold modifier. Komatsu, M. et al. EMBO J. 8 April 2004 (doi:10.1038/sj.emboj.7600205)

Ubiquitin-like proteins (UBLs), which resemble ubiquitin structurally, have recently been discovered. Komatsu et al. now describe a new UBL protein, Ufm1 (ubiquitin-fold modifier-1). They also identified Ubc5 and Ufc1, which function as E1-like (activating) and E2-like (conjugating) enzymes, respectively. Ufm1 is processed to expose a glycine residue that is necessary for its conjugation to a target protein prior to activation by Ubc5.

Apoptosis

The PIDDosome, a protein complex implicated in activation of caspase-2 in response to genotoxic stress. Tinel, A. & Tschopp, J. Science 8 April 2004 (doi:10.1126/science.1095432)

Tinel and Tschopp have identified a protein complex that is responsible for the activation of caspase-2, which is involved in stress-induced apoptosis. Caspase-2 — is activated during complex formation with the adaptor protein RAIDD and the p53-induced protein PIDD. Increased PIDD expression causes the spontaneous activation of caspase-2 and enhanced sensitivity to apoptosis in response to genotoxic stimuli.