Organellar proteins are sorted by cargo receptors on the way to their final destination. However,... more Organellar proteins are sorted by cargo receptors on the way to their final destination. However, receptors for proteins that are destined for the protein storage vacuole (PSV) are largely unknown. In this study, we investigated the biological role that Arabidopsis thaliana receptor homology region transmembrane domain ring H2 motif protein (AtRMR) 1 plays in protein trafficking to the PSV. AtRMR1 mainly colocalized to the prevacuolar compartment of the PSV, but a minor portion also localized to the Golgi complex. The coexpression of AtRMR1 mutants that were localized to the Golgi complex strongly inhibited the trafficking of phaseolin to the PSV and caused accumulation of phaseolin in the Golgi complex or its secretion. Co-immunoprecipitation and in vitro binding assays revealed that the lumenal domain of AtRMR1 interacts with the COOH-terminal sorting signal of phaseolin at acidic pH. Furthermore, phaseolin colocalized with AtRMR1 on its way to the PSV. Based on these results, we propose that AtRMR1 functions as the sorting receptor of phaseolin for its trafficking to the PSV.
Complete sequencing of the Arabidopsis genome a decade ago has facilitated the functional analysi... more Complete sequencing of the Arabidopsis genome a decade ago has facilitated the functional analysis of various biological processes including membrane traffic by which many proteins are delivered to their sites of action and turnover. In particular, membrane traffic between post-Golgi compartments plays an important role in cell signaling, taking care of receptor-ligand interaction and inactivation, which requires secretion, endocytosis, and recycling or targeting to the vacuole for degradation. Here, we discuss recent studies that address the identity of post-Golgi compartments, the machinery involved in traffic and fusion or functionally characterized cargo proteins that are delivered to or pass through post-Golgi compartments. We also provide an outlook on future challenges in this area of research.
Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constric... more Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constrict the plasma membrane (PM) in the division plane. Instead, trans-Golgi network (TGN)-derived membrane vesicles are targeted to the centre of the division plane and generate, by homotypic fusion, the partitioning membrane named cell plate (CP). The CP expands in a centrifugal fashion until its margin fuses with the PM at the cortical division site. Mutant screens in Arabidopsis have identified a cytokinesis-specific syntaxin named KNOLLE and an interacting Sec1/Munc18 (SM) protein named KEULE both of which are required for vesicle fusion during cytokinesis. KNOLLE is only made during M-phase, targeted to the division plane and degraded in the vacuole at the end of cytokinesis. Here we address mechanisms of KNOLLE trafficking and interaction of KNOLLE with different soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor (SNARE) partners and with SM-protein KEULE, ensuring membrane fusion in cytokinesis.
Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constric... more Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constrict the plasma membrane (PM) in the division plane. Instead, trans-Golgi network (TGN)-derived membrane vesicles are targeted to the centre of the division plane and generate, by homotypic fusion, the partitioning membrane named cell plate (CP). The CP expands in a centrifugal fashion until its margin fuses with the PM at the cortical division site. Mutant screens in Arabidopsis have identified a cytokinesis-specific syntaxin named KNOLLE and an interacting Sec1/Munc18 (SM) protein named KEULE both of which are required for vesicle fusion during cytokinesis. KNOLLE is only made during M-phase, targeted to the division plane and degraded in the vacuole at the end of cytokinesis. Here we address mechanisms of KNOLLE trafficking and interaction of KNOLLE with different soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor (SNARE) partners and with SM-protein KEULE, ensuring membrane fusion in cytokinesis.
Organellar proteins are sorted by cargo receptors on the way to their final destination. However,... more Organellar proteins are sorted by cargo receptors on the way to their final destination. However, receptors for proteins that are destined for the protein storage vacuole (PSV) are largely unknown. In this study, we investigated the biological role that Arabidopsis thaliana receptor homology region transmembrane domain ring H2 motif protein (AtRMR) 1 plays in protein trafficking to the PSV. AtRMR1 mainly colocalized to the prevacuolar compartment of the PSV, but a minor portion also localized to the Golgi complex. The coexpression of AtRMR1 mutants that were localized to the Golgi complex strongly inhibited the trafficking of phaseolin to the PSV and caused accumulation of phaseolin in the Golgi complex or its secretion. Co-immunoprecipitation and in vitro binding assays revealed that the lumenal domain of AtRMR1 interacts with the COOH-terminal sorting signal of phaseolin at acidic pH. Furthermore, phaseolin colocalized with AtRMR1 on its way to the PSV. Based on these results, we propose that AtRMR1 functions as the sorting receptor of phaseolin for its trafficking to the PSV.
Complete sequencing of the Arabidopsis genome a decade ago has facilitated the functional analysi... more Complete sequencing of the Arabidopsis genome a decade ago has facilitated the functional analysis of various biological processes including membrane traffic by which many proteins are delivered to their sites of action and turnover. In particular, membrane traffic between post-Golgi compartments plays an important role in cell signaling, taking care of receptor-ligand interaction and inactivation, which requires secretion, endocytosis, and recycling or targeting to the vacuole for degradation. Here, we discuss recent studies that address the identity of post-Golgi compartments, the machinery involved in traffic and fusion or functionally characterized cargo proteins that are delivered to or pass through post-Golgi compartments. We also provide an outlook on future challenges in this area of research.
Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constric... more Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constrict the plasma membrane (PM) in the division plane. Instead, trans-Golgi network (TGN)-derived membrane vesicles are targeted to the centre of the division plane and generate, by homotypic fusion, the partitioning membrane named cell plate (CP). The CP expands in a centrifugal fashion until its margin fuses with the PM at the cortical division site. Mutant screens in Arabidopsis have identified a cytokinesis-specific syntaxin named KNOLLE and an interacting Sec1/Munc18 (SM) protein named KEULE both of which are required for vesicle fusion during cytokinesis. KNOLLE is only made during M-phase, targeted to the division plane and degraded in the vacuole at the end of cytokinesis. Here we address mechanisms of KNOLLE trafficking and interaction of KNOLLE with different soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor (SNARE) partners and with SM-protein KEULE, ensuring membrane fusion in cytokinesis.
Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constric... more Cytokinesis separates the forming daughter cells. Higher plants have lost the ability to constrict the plasma membrane (PM) in the division plane. Instead, trans-Golgi network (TGN)-derived membrane vesicles are targeted to the centre of the division plane and generate, by homotypic fusion, the partitioning membrane named cell plate (CP). The CP expands in a centrifugal fashion until its margin fuses with the PM at the cortical division site. Mutant screens in Arabidopsis have identified a cytokinesis-specific syntaxin named KNOLLE and an interacting Sec1/Munc18 (SM) protein named KEULE both of which are required for vesicle fusion during cytokinesis. KNOLLE is only made during M-phase, targeted to the division plane and degraded in the vacuole at the end of cytokinesis. Here we address mechanisms of KNOLLE trafficking and interaction of KNOLLE with different soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein (SNAP) receptor (SNARE) partners and with SM-protein KEULE, ensuring membrane fusion in cytokinesis.
Uploads