<i>Arabidopsis</i> HAP2/GCS1 is a gamete fusion protein homologous to somatic and viral fusogens

Valansi, Clari; Moi, David; Leikina, Evgenia; Matveev, Elena; Graña, Martín; Chernomordik, Leonid V.; Romero, Héctor; Aguilar, Pablo S.; Podbilewicz, Benjamin

doi:10.1083/jcb.201610093

Cited by 102 publications

(166 citation statements)

References 46 publications

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“…A stem region connects these globular domains to two transmembrane domains in flaviviruses 8 or a single-pass transmembrane domain and a cytoplasmic domain in eukaryotes. Although sequence homology is not detectable among class II fusogens from different virus families or with HAP2, similar three-dimensional structures and functions suggest that they diverged from a common ancestor [3][4][5] . As with viral class II proteins, HAP2 functions uni-directionally.…”

Section: Introductionmentioning

confidence: 92%

“…Recent work on HAP2 from the green alga Chlamydomonas, the flowering plant Arabidopsis, and the ciliate Tetrahymena shows that HAP2 is, in common with fusogens used by certain enveloped viruses to enter host cells, a class II fusion glycoprotein [3][4][5] . Class II fusogens are characterized by their mainly β -sheet-containing-domains I, II, and III (referred to here as D1, D2, and D3) 6,7 .…”

Section: Introductionmentioning

confidence: 99%

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Fusion surface structure, function, and dynamics of gamete fusogen HAP2

Feng

Dong

Pinello³

et al. 2018

Preprint

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HAP2 is a class II gamete fusogen in many eukaryotic kingdoms. A crystal structure of Chlamydomonas HAP2 shows a trimeric fusion state. Domains D1, D2.1 and D2.2 line the 3-fold axis; D3 and a stem pack against the outer surface. Surprisingly, hydrogen-deuterium exchange shows that surfaces of D1, D2.2 and D3 closest to the 3-fold axis are more dynamic than exposed surfaces. Three fusion helices in the fusion loop of each monomer expose hydrophobic residues at the trimer apex that are splayed from the 3-fold axis, leaving a solventfilled cavity between the fusion loops in each monomer. At the base of the long fusion loop, Arg185 docks in a carbonyl cage. Comparisons to other structures, dynamics, and the greater effect on Chlamydomonas gamete fusion of mutation of axis-proximal than axis-distal fusion helices suggest that the apical portion of each monomer could tilt toward the 3-fold axis with merger of the fusion helices into a common fusion surface.All rights reserved. No reuse allowed without permission.

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Section: Introductionmentioning

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Fusion surface structure, function, and dynamics of gamete fusogen HAP2

Feng

Dong

Pinello³

et al. 2018

Preprint

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“…Importantly, these proteins become eliminated from the plasma membrane after gamete fusion, and this process correlates with a reduction in the fusogenic capacity of the gametic cell so as to prevent polygamy (Liu et al, ). Also in flowering plants, HAP2/GCS1 has been reported to be an essential sperm component required for gamete fusion (Mori et al, ; Valansi et al, ; von Besser et al, ). The corresponding egg cell plasma membrane localized factor that is essential for the gamete fusion is not yet known but we speculate that similar mechanisms might operate as well in flowering plants.…”

Section: Introductionmentioning

confidence: 99%

New advances and future directions in plant polyspermy

Tekleyohans

Groß‐Hardt

2019

Molecular Reproduction Devel

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Plants have evolved a battery of mechanisms that potentially act as polyspermy barriers. Supernumerary sperm fusion to one egg cell has consequently long remained a hypothetical concept. The recent discovery that polyspermy in flowering plants is not lethal but generates viable triploid plants is a game changer affecting the field of developmental biology, evolution, and plant breeding. The establishment of protocols to artificially induce polyspermy together with the development of a high‐throughput assay to identify and trace polyspermic events in planta now provide powerful tools to unravel mechanisms of polyspermy regulation. These achievements are likely to open new avenues for animal polyspermy research as well, where forward genetic approaches are hampered by the fatal outcome of supernumerary sperm fusion.

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“…Regarding to GCS1/HAP2, it has been reported that GCS1/HAP2 is homologous to viral class II fusion protein (Fédry et al 2017;Pinello et al 2017;Valansi et al 2017). To achieve somatic cell fusion of mammalian cells, ectopic expression of Arabidopsis GCS1/HAP2 was required for both cells, indicating bilateral homotypic mechanism of GCS1/HAP2.…”

mentioning

confidence: 99%

“…To achieve somatic cell fusion of mammalian cells, ectopic expression of Arabidopsis GCS1/HAP2 was required for both cells, indicating bilateral homotypic mechanism of GCS1/HAP2. Since GCS1/HAP in flowering plants is specific to male gametes, it has been hypothesized that female gametes express a GCS1/HAP2 family protein that interacts with sperm GCS1/HAP2 as the bilateral mechanism for fertilization (Valansi et al 2017). When a secretory-type GCS1/HAP2 (named GAH), in which the single transmembrane region of GCS1/ HAP2 was replaced by GFP, was ectopically expressed in Arabidopsis egg cell, occasional blockade of double fertilization was observed (Mori 2014).…”

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confidence: 99%

Isolation of GFP-tagged plasma membrane protein from Arabidopsis egg cells

Igawa

Yamada

Sawada

et al. 2017

Plant Biotechnology

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Angiosperms possess a double fertilization system for sexual reproduction. Double fertilization is regulated by interactions among proteins localized in the plasma membrane of each sex gamete. A few plasma membrane resident proteins regulating double fertilization have been identified in male gametes. In contrast, no fertilization regulators in female gamete plasma membrane have been identified, largely due to difficulties in the isolation and collection of female gametes. We had produced Arabidopsis transgenic plant pDD45::GFP-AtPIP2;1 where the egg cell plasma membrane was specifically labeled with GFP ). The protein extract derived from approximately 200 pistils, which contained unfertilized and mature egg cells, was subjected to immunoprecipitation using anti-GFP antibody. As a result, both GFP and AtPIP2;1 were specifically detected in immunoprecipitated proteins from pistil tissues of pDD45::GFP-AtPIP2;1 transgenic plant, but not in those of wild type pistils. It was revealed that specific proteins expressed in the egg cells were successfully isolated from pistil cell population. The method described here showed the feasibility of isolating specific egg cell plasma membrane protein without gamete isolation and collection procedures.

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Arabidopsis HAP2/GCS1 is a gamete fusion protein homologous to somatic and viral fusogens

Abstract: HAP2/GCS1 is essential for gamete fusion in plants, invertebrates, and protists. Valansi et al. demonstrate that a plant HAP2 is an authentic fusion protein that can fuse animal cells.

Cited by 102 publications

References 46 publications

Fusion surface structure, function, and dynamics of gamete fusogen HAP2

Fusion surface structure, function, and dynamics of gamete fusogen HAP2

New advances and future directions in plant polyspermy

Isolation of GFP-tagged plasma membrane protein from Arabidopsis egg cells

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