Abstract
Tetraspanins (TETs) function as key molecular scaffolds for surface signal recognition and transduction via the assembly of tetraspanin-enriched microdomains. TETs’ function in mammalian has been intensively investigated for the organization of multimolecular membrane complexes, regulation of cell migration and cellular adhesion, whereas plant TET studies lag far behind. Animal and plant TETs share similar topologies, despite the hallmark of “CCG” in the large extracellular loop of animal TETs, plant TETs contain a plant specific GCCK/RP motif and more conserved cysteine residues. Here, we showed that the GCCK/RP motif is responsible for TET protein association with the plasma membrane. Moreover, the conserved cysteine residues located within or neighboring the GCCK/RP motif are both crucial for TET anchoring to membrane. During virus infection, the intact TET3 protein enhanced but GCCK/RP motif or cysteine residues-deficient TET3 variants abolished the cell-to-cell movement capability of virus. This study provides cellular evidence that the GCCK/RP motif and the conserved cysteine residues are the primary determinants for the distribution and function of TET proteins in Arabidopsis.
Highlights
The plasma membrane (PM) is a permeable membrane system, which provides a platform of signal activation for pathogen entry or defense to pathogens (Nathalie and Bouhidel, 2014; Heinlein, 2015)
To understand the subcellular localization of Arabidopsis TETs, green fluorescent protein (GFP) was fused to the C-terminus of TET proteins (TET2, 3, 4, 7, 8, and 9), under the control of the constitutive Cauliflower mosaic virus 35S (CaMV35S) promoter, which was based on the protein fusion criteria of previous reported TET proteins (Boavida et al, 2013)
Subcellular visualization showed that TET2, 3, 4, 7, 8, and 9 mainly targeted to the PM in Arabidopsis root and leaf cells (Figure 1C and Supplementary Figure 2B), and they were found within endosomes or vacuole-like structures in the cytosol (Figure 1C)
Summary
The plasma membrane (PM) is a permeable membrane system, which provides a platform of signal activation for pathogen entry or defense to pathogens (Nathalie and Bouhidel, 2014; Heinlein, 2015). Viruses take advantage of cellular membrane to infect host cells in various ways (Burckhardt and Greber, 2009). Clathrin-mediated endocytosis is the major cellular entry pathway for the enveloped virus fusion with PM (Marsh and Helenius, 2006; Miyauchi et al, 2009; Mudhakir and Harashima, 2009). PM is not a homogeneous sheet with associated proteins and lipids (Jacobson et al, 2019). The membrane lipid rafts are consisted of liquid-ordered membrane nanoscale domains (
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