Targeting of OSBP-related protein 3 (ORP3) to endoplasmic reticulum and plasma membrane is controlled by multiple determinants |
| |
Authors: | Lehto Markku Hynynen Riikka Karjalainen Katja Kuismanen Esa Hyvärinen Kati Olkkonen Vesa M |
| |
Institution: | Department of Molecular Medicine, National Public Health Institute, Biomedicum, P.O. Box 104, FI-00251 Helsinki, Finland. |
| |
Abstract: | The intracellular targeting determinants of oxysterol binding protein (OSBP)-related protein 3 (ORP3) were studied using a series of truncated and point mutated constructs. The pleckstrin homology (PH) domain of ORP3 binds the phosphoinositide-3-kinase (PI3K) products, PI(3,4)P2 and PI(3,4,5)P3. A functional PH domain and flanking sequences are crucial for the plasma membrane (PM) targeting of ORP3. The endoplasmic reticulum (ER) targeting of ORP3 is regulated the by a FFAT motif (EFFDAxE), which mediates interaction with VAMP-associated protein (VAP)-A. The targeting function of the FFAT motif dominates over that of the PH domain. In addition, the exon 10/11 region modulates interaction of ORP3 with the ER and the nuclear membrane. Analysis of a chimeric ORP3:OSBP protein suggests that ligand binding by the C-terminal domain of OSBP induces allosteric changes that activate the N-terminal targeting modules of ORP3. Notably, over-expression of ORP3 together with VAP-A induces stacked ER membrane structures also known as organized smooth ER (OSER). Moreover, lipid starvation promotes formation of dilated peripheral ER (DPER) structures dependent on the ORP3 protein. Based on the present data, we introduce a model for the inter-relationships of the functional domains of ORP3 in the membrane targeting of the protein. |
| |
Keywords: | DPER dilated peripheral ER EM electron microscopy ER endoplasmic reticulum FFAT motif two phenylalanines in an acidic tract motif IF immunofluorescence OR OSBP-related 25OH 25-hydroxycholesterol ORP OSBP-related protein OSBP oxysterol binding protein OSER organized smooth endoplasmic reticulum PH domain pleckstrin homology domain PIP phosphoinositide PI3K phosphoinositide-3-kinase PM plasma membrane VAP-A VAMP-associated membrane protein-A |
本文献已被 ScienceDirect PubMed 等数据库收录! |
|