Effects of Vesl/Homer proteins on intracellular signaling.

The clustering of signaling molecules at specialized cellular sites allows cells to effectively convert extracellular signals into intracellular signals and to produce a concerted functional output with specific temporal and spatial patterns. A prime example for these molecules and their effects on cellular signaling are the postsynaptic density proteins of the central nervous system. Recently, one group of these proteins, the Vesl/Homer protein family has received increased attention because of its unique molecular properties that allow both the clustering and functional modulation of a plethora of different binding proteins. Within multiprotein signaling complexes, Vesl/Homer proteins influence proteins as diverse as metabotropic glutamate receptors; transient receptor potential channels; intra-cellular calcium channels; the scaffolding protein, Shank; small GTPases; transcription factors; and cytoskeletal proteins. Furthermore, interaction with such functionally relevant proteins also links Vesl/Homer proteins indirectly to an even larger group of cellular effector proteins, putting the Vesl/Homer proteins at the crossroads of several critical intracellular signaling processes. In addition to the initial reports of Vesl/Homer protein expression in the central nervous system, members of this protein family have now been identified in other excitable cells in various muscle types and in a large number of nonexcitable cells. The widespread expression of Vesl/Homer proteins in different organs and their functional importance in cellular protein signaling complexes is further evidenced by their conservation in organisms from Drosophila to humans.