Plasma Membrane Localization of Solanum tuberosum Remorin from Group 1, Homolog 3 Is Mediated by Conformational Changes in a Novel C-Terminal Anchor and Required for the Restriction of Potato Virus X Movement    

Abstract

The formation of plasma membrane (PM) microdomains plays a crucial role in the regulation of membrane signaling and trafficking. Remorins are a plant-specific family of proteins organized in six phylogenetic groups, and Remorins of group 1 are among the few plant proteins known to specifically associate with membrane rafts. As such, they are valuable to understand the molecular bases for PM lateral organization in plants. However, little is known about the structural determinants underlying the specific association of group 1 Remorins with membrane rafts. We used a structure-function approach to identify a short C-terminal anchor (RemCA) indispensable and sufficient for tight direct binding of potato (Solanum tuberosum) REMORIN 1.3 (StREM1.3) to the PM. RemCA switches from unordered to a-helical structure in a nonpolar environment. Protein structure modeling indicates that RemCA folds into a tight hairpin of amphipathic helices. Consistently, mutations reducing RemCA amphipathy abolished StREM1.3 PM localization. Furthermore, RemCA directly binds to biological membranes in vitro, shows higher affinity for Detergent-Insoluble Membranes lipids, and targets yellow fluorescent protein to Detergent-Insoluble Membranes in vivo. Mutations in RemCA resulting in cytoplasmic StREM1.3 localization abolish StREM1.3 function in restricting potato virus X movement. The mechanisms described here provide new insights on the control and function of lateral segregation of plant PM.

Grain setting defect1, Encoding a Remorin Protein, Affects the Grain Setting in Rice through Regulating Plasmodesmatal Conductance

“…The nonconserved N-terminal residues, which are predicted to be intrinsically disordered ) with a three-dimensional structure that varies depending on physiological conditions (Dyson and Wright, 2005), are believed to play an important role in regulation, signaling, and control through high-specificity, low-affinity protein-protein interactions (Sickmeier et al, 2007). Although remorins have been postulated to affect PD conductance in previous studies, their biological functions remained ambiguous because of the lack of phenotypic consequences associated with their expression (Raffaele et al, 2009;Perraki et al, 2012). Overexpression of GSD1 from T-DNA disruption of the promoter reduced PD conductance, whereas the phenotype of the gsd1-D mutant indicates that variations in the expression level of GSD1 could regulate grain filling.…”

The Intrinsically Disordered N-terminal Region of AtREM1.3 Remorin Protein Mediates Protein-Protein Interactions

“…The complete C-terminal region (residues 78 -190) unfortunately could not be successfully expressed and purified. Interestingly, the C-terminal 28 residues of potato remorin StREM1.3 are responsible for plasma membrane attachment (6). Based on sequence comparisons, these 28 terminal residues are probably also required for AtREM1.3 plasma membrane attachment.…”

“…3), in accordance with the results obtained by CD and limited proteolysis. This model resembles a recently published homology model of the potato remorin StREM1.3, which also describes an ␣-helical C-terminal domain (6). Subsequently, we searched for regions within the model, which may be prone to mediate protein interactions using the PPI-Pred and ProMate programs.…”

“…These proteins evolved in all land plants, including ferns and mosses and constitute a multigene family that comprises six subgroups with no significant sequence similarity to other described proteins or domains (5). All remorins are characterized by the presence of a conserved C-terminal region (Pfam domain Remorin_C; PF03763) that encodes a predicted coiled-coil motif and a dynamic membrane-anchoring motif (6). Additionally, almost all groups harbor a highly diverse N-terminal region, which is predicted to be intrinsically disordered and to harbor most phosphorylation sites (7).…”

ORM Expression Alters Sphingolipid Homeostasis and Differentially Affects Ceramide Synthase Activities

“…Sphingolipids also are highly enriched in detergent-insoluble membrane fractions of the plasma membrane that form microdomains for proteins with important cell surface activities, including cell wall biosynthesis and hormone transport (Cacas et al, , 2016Perraki et al, 2012;Bayer et al, 2014). In addition, sphingolipids, particularly those with very-long-chain fatty acids (VLCFAs), are integrally associated with Golgi-mediated protein trafficking that underlies processes related to the growth of plant cells (Bach et al, 2008(Bach et al, , 2011Markham et al, 2011;Melser et al, 2011).…”