Cholesterol Research Today is a free monthly online journal that collates and summarizes the latest research about Cholesterol, including details on high cholesterol, hdl, ldl, diet, risks. | ||||||||
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Characterization of the sterol-binding domain of oxysterol-binding protein (OSBP)-related protein 4 reveals a novel role in vimentin organization.Wyles JP, Perry RJ, Ridgway ND The Atlantic Research Centre, Department of Pediatrics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7. Oxysterol-binding protein (OSBP) and OSBP-related protein 4 (ORP4; also designated OSBP2 and HLM) are implicated in sterol-transport and/or sensing via binding to protein partners. The aggregation of vimentin by an N-terminal-truncated variant of ORP4 (ORP4S), but not full-length ORP4L, suggested a functional interaction with this intermediate filament. Herein, we identify ORP4 domains that interact with vimentin, and determine how sterols and OSBP influence this activity. In CHO cells, ORP4L co-localized with filamentous vimentin but extensive remodeling of vimentin filaments required mutation of a leucine repeat motif (amino acids 361-382) adjacent to the oxysterol-binding domain. Similarly, the absence of the leucine repeat in ORP4S 418-878 resulted in co-localization with aggregated vimentin filaments, suggesting that both the sterol-binding domain and leucine repeat are involved. Transient expression of OSBP leucine repeat mutants also promoted vimentin aggregation by a mechanism involving heterodimerization with ORP4L. Glutathione S-transferase (GST)-ORP4 380-878 bound vimentin, cholesterol and 25-hydroxycholesterol in vitro. However, sterol-binding or a mutation that ablated sterol-binding did not influence the interaction of GST-ORP4 with vimentin. Thus the sterol-binding domain of ORP4 binds vimentin, cholesterol and oxysterols, and interacts with the filamentous vimentin network. Published 6 April 2007 in Exp Cell Res, 313(7): 1426-37.
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