Molecular mechanism underlying the association of Coronin-7 with Golgi membranes

Abstract

Coronin-7 (Crn7) is a ubiquitous mammalian WD40-repeat protein that localizes to the Golgi complex, interacts with AP-1 adaptor complex via binding of a tyrosine-288-based sorting signal to the mu1-subunit of AP-1, and participates in the maintenance of the Golgi structure and function. Here, we define the requirements for the recruitment of Crn7 from the cytosol to the Golgi. We establish that Src activity is indispensable for the interaction of Crn7 with Golgi membranes. Crn7 binds Src in vivo and can be phosphorylated by recombinant Src in vitro. We demonstrate that tyrosine-758 is the major Src phosphorylation site. Further, to be targeted to membranes Crn7 requires the presence of cargo in the Golgi complex. Finally, downregulation of the mu1-subunit of AP-1 leads to the dispersal of Crn7 from the Golgi membranes. We propose a mechanism whereby sequential events of protein interaction and posttranslational modification result in the membrane targeting of Crn7.

Unraveling the enigma: progress towards understanding the coronin family of actin regulators

“…Targeting of Coro7 to the Golgi membrane is reliant on tyrosine phosphorylation of Coro7 57 . Redistribution of Coro7 to the cytosol following treatment with the Src Kinase inhibitor SU6556 implicates Src as the key kinase in this phosphorylation dependent membrane targeting, but further studies of a potential Src-Coronin 7 interaction are needed to confirm this and to enhance our understanding of Coro7s function at the Golgi.…”

Signaling Circuits on the Golgi Complex

“…Cnr7 appears to act as a mediator of cargo‐vesicle formation at the TGN, downstream of the AP1 interaction with cargo, but upstream of PKD‐dependent membrane fission . Depletion of Crn7 by RNA interference results in Golgi breakdown and accumulation of arrested cargo proteins . Crn7 binds Src in vivo and can be phosphorylated by recombinant Src in vitro at Tyr758, a modification that is essential for the interaction of Crn7 with Golgi membranes, and is correlated with the arrest of cargo at the Golgi complex under Src inhibition .…”

“…Depletion of Crn7 by RNA interference results in Golgi breakdown and accumulation of arrested cargo proteins . Crn7 binds Src in vivo and can be phosphorylated by recombinant Src in vitro at Tyr758, a modification that is essential for the interaction of Crn7 with Golgi membranes, and is correlated with the arrest of cargo at the Golgi complex under Src inhibition . However, direct and specific effects of Src phosphorylation on Cnr7 in vivo have not been demonstrated.…”

The Wilms’ tumor suppressor Wt1 regulates Coronin 1B expression in the epicardium

“…A recent study has revealed that Coronin 1C interacts with Rab27a to regulate the internalization of membranes in insulin-secreting cell lines [13]. Coronin 7 has been shown to be associated with Golgi membranes and knockdown of this protein by small interfering RNA results in dramatic changes in the Golgi morphology and function [14].…”