Cell Biology

Phosphorylation Inside-Out

Science Signaling  22 Jul 2008:
Vol. 1, Issue 29, pp. ec265
DOI: 10.1126/scisignal.129ec265

A signaling pathway called the Hippo pathway has important roles in the control of tissue organization in development and in the regulation of organ size in the fruit fly. Hippo is a protein kinase that appears to pass signals from atypical cadherin molecules Fat and Dachsous at the cell surface to another intracellular kinase, Warts, which then regulates a transcriptional coactivator. Another protein somewhat distantly related to the protein kinases, Four-jointed, has also been implicated genetically in the pathway. Ishikawa et al. provide evidence that Four-jointed, which is localized to the Golgi complex, is indeed a kinase and that it appears to phosphorylate the cadherin domains of Fat and Dachsous, which will become extracellular domains at the cell surface.

H. O. Ishikawa, H. Takeuchi, R. S. Haltiwanger, K. D. Irvine, Four-jointed is a Golgi kinase that phosphorylates a subset of cadherin domains. Science 321, 401-404 (2008). [Abstract] [Full Text]