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SMIM1, carrier of the Vel blood group, is a tail-anchored transmembrane protein and readily forms homodimers in a cell-free system

Nylander, Anja LU orcid ; Leznicki, Pawel ; Vidovic, Karina LU ; High, Stephen and Olsson, Martin L. LU orcid (2020) In Bioscience Reports 40(5).
Abstract

Antibodies to the Vel blood group antigen can cause adverse hemolytic reactions unless Vel-negative blood units are transfused. Since the genetic background of Vel-negativity was discovered in 2013, DNA-based typing of the 17-bp deletion causing the phenotype has facilitated identification of Vel-negative blood donors. SMIM1, the gene underlying Vel, encodes a 78-amino acid erythroid transmembrane protein of unknown function. The transmembrane orientation of SMIM1 has been debated since experimental data supported both the N- and C-termini being extracellular. Likewise, computational predictions of its orientation were divided and potential alternatives such as monotopic or dual-topology have been discussed but not investigated. We used... (More)

Antibodies to the Vel blood group antigen can cause adverse hemolytic reactions unless Vel-negative blood units are transfused. Since the genetic background of Vel-negativity was discovered in 2013, DNA-based typing of the 17-bp deletion causing the phenotype has facilitated identification of Vel-negative blood donors. SMIM1, the gene underlying Vel, encodes a 78-amino acid erythroid transmembrane protein of unknown function. The transmembrane orientation of SMIM1 has been debated since experimental data supported both the N- and C-termini being extracellular. Likewise, computational predictions of its orientation were divided and potential alternatives such as monotopic or dual-topology have been discussed but not investigated. We used a cell-free system to explore the topology of SMIM1 when synthesized in the endoplasmic reticulum (ER). SMIM1 was tagged with an opsin-derived N-glycosylation reporter at either the N- or C-terminus and synthesized in vitro using rabbit reticulocyte lysate supplemented with canine pancreatic microsomes as a source of ER membrane. SMIM1 topology was then determined by assessing the N-glycosylation of its N- or C-terminal tags. Complementary experiments were carried out by expressing the same SMIM1 variants in HEK293T/17 cells and establishing their membrane orientation by immunoblotting and flow cytometry. Our data consistently indicate that SMIM1 has its short C-terminus located extracellularly and that it most likely belongs to the tail-anchored class of membrane proteins with the bulk of the polypeptide located in the cytoplasm. Having established its membrane orientation in an independent model system, future work can now focus on functional aspects of SMIM1 as a potential regulator of erythropoiesis.

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Please use this url to cite or link to this publication:
author
; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Bioscience Reports
volume
40
issue
5
article number
BSR20200318
publisher
Portland Press
external identifiers
  • pmid:32301496
  • scopus:85084379859
ISSN
0144-8463
DOI
10.1042/BSR20200318
project
Further investigation into the structure and function of SMIM1, a newly discovered erythroid transmembrane protein
language
English
LU publication?
yes
id
d0cf2761-b4ed-4367-aad4-7900297b2ed1
date added to LUP
2020-06-02 15:51:06
date last changed
2024-05-01 11:20:38
@article{d0cf2761-b4ed-4367-aad4-7900297b2ed1,
  abstract     = {{<p>Antibodies to the Vel blood group antigen can cause adverse hemolytic reactions unless Vel-negative blood units are transfused. Since the genetic background of Vel-negativity was discovered in 2013, DNA-based typing of the 17-bp deletion causing the phenotype has facilitated identification of Vel-negative blood donors. SMIM1, the gene underlying Vel, encodes a 78-amino acid erythroid transmembrane protein of unknown function. The transmembrane orientation of SMIM1 has been debated since experimental data supported both the N- and C-termini being extracellular. Likewise, computational predictions of its orientation were divided and potential alternatives such as monotopic or dual-topology have been discussed but not investigated. We used a cell-free system to explore the topology of SMIM1 when synthesized in the endoplasmic reticulum (ER). SMIM1 was tagged with an opsin-derived N-glycosylation reporter at either the N- or C-terminus and synthesized in vitro using rabbit reticulocyte lysate supplemented with canine pancreatic microsomes as a source of ER membrane. SMIM1 topology was then determined by assessing the N-glycosylation of its N- or C-terminal tags. Complementary experiments were carried out by expressing the same SMIM1 variants in HEK293T/17 cells and establishing their membrane orientation by immunoblotting and flow cytometry. Our data consistently indicate that SMIM1 has its short C-terminus located extracellularly and that it most likely belongs to the tail-anchored class of membrane proteins with the bulk of the polypeptide located in the cytoplasm. Having established its membrane orientation in an independent model system, future work can now focus on functional aspects of SMIM1 as a potential regulator of erythropoiesis.</p>}},
  author       = {{Nylander, Anja and Leznicki, Pawel and Vidovic, Karina and High, Stephen and Olsson, Martin L.}},
  issn         = {{0144-8463}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{Portland Press}},
  series       = {{Bioscience Reports}},
  title        = {{SMIM1, carrier of the Vel blood group, is a tail-anchored transmembrane protein and readily forms homodimers in a cell-free system}},
  url          = {{http://dx.doi.org/10.1042/BSR20200318}},
  doi          = {{10.1042/BSR20200318}},
  volume       = {{40}},
  year         = {{2020}},
}