Editors' ChoiceChannels

More Versatility of Homer

Science's STKE  26 Nov 2002:
Vol. 2002, Issue 160, pp. tw441-TW441
DOI: 10.1126/stke.2002.160.tw441

Homer proteins have been characterized as adaptor proteins in signaling complexes associated with metabotropic glutamate receptors. Homer proteins bind both the receptor and inositol 1,4,5-trisphosphate receptors in these complexes. Noting that Ryanodine receptor type 1 (RyR1) also has a putative Homer-binding sequence, Feng et al. explored the functional relation of these proteins. Endogenous Homer proteins could be immunoprecipitated with RyR1 from extracts of rat skeletal muscle. Recordings from single RyR1 channels reconstituted in bilayer lipid membranes showed that Homer proteins enhanced the open probability of the RyR1 channel. Assays with sarcoplasmic reticulum vesicles from skeletal muscle showed that Homer proteins increased efficacy of Ca2+ and caffeine in activating RyR1. Although the truncated, short form of Homer1 is thought to function in a dominant-negative manner in some systems, both the long and short forms of Homer1 had similar effects on the RyR1 channel. The authors discuss this new role of Homer in regulating the gain of excitation-contraction coupling in muscle cells. For more on Homer, see the STKE Review by Fagni et al.

W. Feng, J. Tu, T. Yang, P. S. Vernon, P. D. Allen, P. F. Worley, I. N. Pessah. Homer regulates gain of ryanodine receptor type 1 channel complex. J. Biol. Chem. 277, 44722-44730 (2002). [Abstract] [Full Text]

L. Fagni, P. F. Worley, F. Ango, Homer as both a scaffold and transduction molecule. Science's STKE (2002), http://stke.sciencemag.org/cgi/content/full/sigtrans;2002/137/re8 [Abstract] [Full Text]