In Vitro
            Acute Ischemic Injury Altered Human Brain Endothelial MMP‐9 Activity and Associated Cell Surface Adhesion Protein Expression in Part by S1PR Type 1 Activation

Signal regulatory protein SIRPγ (CD172G) is expressed on the surface of lymphocytes where it acts by engaging its ligand, CD47. SIRPG, which encodes SIRPγ, contains a non-synonymous coding variant, rs6043409, which is significantly associated with risk for type 1 diabetes. SIRPG produces multiple transcript isoforms via alternative splicing, all encoding potentially functional proteins. We show that rs6043409 alters a predicted exonic splicing enhancer, resulting in significant shifts in the distribution of SIRPG transcript isoforms. All of these transcript isoforms produced protein upon transient expression in vitro. However, CRISPR targeting of one of the alternatively spliced exons in SIRPG eliminated all SIRPγ expression in Jurkat T cells. These targeted cells formed fewer cell-cell conjugates with each other than with wild type Jurkat cells, expressed reduced levels of genes associated with CD47 signaling and had significantly increased levels of cell surface CD47. In primary CD4+ and CD8+ T cells cell surface SIRPγ levels in response to anti-CD3 stimulation varied quantitatively by rs6043409 genotype. Our results suggest that SIRPG is the most likely causative gene for type 1 diabetes risk in the 20p13 region and highlight the role of alternative splicing in lymphocytes in mediating the genetic risk for autoimmunity.

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Envelope-Dependent, Cyclophilin-Independent Effects of Glycosaminoglycans on Human Immunodeficiency Virus Type 1 Attachment and Infection

Journal of Virology ◽

10.1128/jvi.76.12.6332-6343.2002 ◽

2002 ◽

Vol 76 (12) ◽

pp. 6332-6343 ◽

Cited By ~ 88

Author(s):

Yi-jun Zhang ◽

Theodora Hatziioannou ◽

Trinity Zang ◽

Douglas Braaten ◽

Jeremy Luban ◽

...

Keyword(s):

Human Immunodeficiency Virus ◽

Cell Surface ◽

Human Immunodeficiency Virus Type ◽

Virus Type ◽

Target Cells ◽

Independent Manner ◽

Immunodeficiency Virus ◽

Hiv 1

ABSTRACT Cell surface glycosaminoglycans (GAGs), in particular heparan sulfate (HS), have been proposed to mediate the attachment of human immunodeficiency virus type 1 (HIV-1) to target cells prior to virus entry, and both the viral gp120 envelope protein and virion-associated cyclophilin A (CypA) have been shown to directly interact with HS and its analogues. To determine the role of GAGs in HIV attachment and infection, we generated HIV-susceptible derivatives of CHO cell lines that either express high levels of GAGs (CHO-K1) or lack GAGs (pgsA745). Using a panel of HIV-1 envelopes, we found that cell surface GAG-mediated effects on virion attachment and infection vary in an envelope strain-dependent but coreceptor-independent manner. In fact, cell surface GAG-mediated enhancement of infection is confined to isolates that contain a highly positively charged V3-loop sequence, while infection by most strains is apparently inhibited by the presence of GAGs. Moreover, the enhancing and inhibitory effects of polycations and polyanions on HIV-1 infection are largely dependent on the presence of cell surface GAGs. These observations are consistent with a model in which GAGs influence in vitro HIV-1 infection primarily by modifying the charge characteristics of the target cell surface. Finally, the effects of GAGs on HIV-1 infection are observed to an equivalent extent whether CypA is present in or absent from virions. Overall, these data exclude a major role for GAGs in mediating the attachment of many HIV-1 strains to target cells via interactions with virion-associated gp120 or CypA.

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Genetic Control of Splicing at SIRPG Modulates Risk of Type 1 Diabetes

10.2337/figshare.17026610.v1 ◽

2021 ◽

Author(s):

Morgan J. Smith ◽

Lucia Pastor ◽

Jeremy R.B. Newman ◽

Patrick Concannon

Keyword(s):

T Cells ◽

Type 1 Diabetes ◽

Alternative Splicing ◽

Cell Surface ◽

Regulatory Protein ◽

Jurkat Cells ◽

Causative Gene ◽

Transcript Isoforms

Signal regulatory protein SIRPγ (CD172G) is expressed on the surface of lymphocytes where it acts by engaging its ligand, CD47. SIRPG, which encodes SIRPγ, contains a non-synonymous coding variant, rs6043409, which is significantly associated with risk for type 1 diabetes. SIRPG produces multiple transcript isoforms via alternative splicing, all encoding potentially functional proteins. We show that rs6043409 alters a predicted exonic splicing enhancer, resulting in significant shifts in the distribution of SIRPG transcript isoforms. All of these transcript isoforms produced protein upon transient expression in vitro. However, CRISPR targeting of one of the alternatively spliced exons in SIRPG eliminated all SIRPγ expression in Jurkat T cells. These targeted cells formed fewer cell-cell conjugates with each other than with wild type Jurkat cells, expressed reduced levels of genes associated with CD47 signaling and had significantly increased levels of cell surface CD47. In primary CD4+ and CD8+ T cells cell surface SIRPγ levels in response to anti-CD3 stimulation varied quantitatively by rs6043409 genotype. Our results suggest that SIRPG is the most likely causative gene for type 1 diabetes risk in the 20p13 region and highlight the role of alternative splicing in lymphocytes in mediating the genetic risk for autoimmunity.

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Faculty Opinions recommendation of The Arabidopsis SOS5 locus encodes a putative cell surface adhesion protein and is required for normal cell expansion.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1011213.183180 ◽

2003 ◽

Author(s):

Ramón Serrano

Keyword(s):

Cell Surface ◽

Cell Expansion ◽

Normal Cell ◽

Surface Adhesion ◽

Adhesion Protein

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Faculty Opinions recommendation of The Arabidopsis SOS5 locus encodes a putative cell surface adhesion protein and is required for normal cell expansion.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1011213.178412 ◽

2003 ◽

Author(s):

Simon McQueen-Mason

Keyword(s):

Cell Surface ◽

Cell Expansion ◽

Normal Cell ◽

Surface Adhesion ◽

Adhesion Protein

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Selective Expression of a Stable Cell Surface Molecule on Type 2 but Not Type 1 Helper T Cells

Journal of Experimental Medicine ◽

10.1084/jem.187.5.787 ◽

1998 ◽

Vol 187 (5) ◽

pp. 787-794 ◽

Cited By ~ 382

Author(s):

Damo Xu ◽

Woon Ling Chan ◽

Bernard P. Leung ◽

Fang-ping Huang ◽

Rachel Wheeler ◽

...

Keyword(s):

T Cells ◽

Cell Surface ◽

Leishmania Major ◽

Flow Cytometric Analysis ◽

Dependent Manner ◽

Cell Surface Molecule ◽

Ifn Γ

T helper cell type 1 (Th1) and 2 (Th2) are central to immune regulation. However, no stable cell surface marker capable of distinguishing and separating these two subsets of CD4+ cells has yet been found. Using differential display PCR, we have identified a gene encoding a cell membrane bound molecule, originally designated ST2L, T1, DER4, or Fit, expressed constitutively and stably on the surface of murine Th2s, but not Th1s even after stimulation with a range of immunological stimuli. Antibody against a peptide derived from ST2L strongly and stably labeled the surface of cloned Th2s but not Th1s, and Th2s but not Th1s derived from naive T cells of ovalbumin T cell receptor–α/β transgenic mice. Three-color single cell flow cytometric analysis shows that cell surface ST2L coexpressed with intracellular interleukin (IL)-4, but not with interferon (IFN)-γ. The antibody selectively lysed Th2s in vitro in a complement-dependent manner. In vivo, it enhanced Th1 responses by increasing IFN-γ production and decreasing IL-4 and IL-5 synthesis. It induced resistance to Leishmania major infection in BALB/c mice and exacerbated collagen-induced arthritis in DBA/1 mice. Thus, ST2L is a stable marker distinguishing Th2s from Th1s and is also associated with Th2 functions. Hence, it may be a target for therapeutic intervention.

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Human Immunodeficiency Virus Type 1 Nef-Induced CD4 Cell Surface Downregulation Is Inhibited by Ikarugamycin

Journal of Virology ◽

10.1128/jvi.75.5.2488-2492.2001 ◽

2001 ◽

Vol 75 (5) ◽

pp. 2488-2492 ◽

Cited By ~ 35

Author(s):

Tianci Luo ◽

Brenda L. Fredericksen ◽

Keiji Hasumi ◽

Akira Endo ◽

J. Victor Garcia

Keyword(s):

Human Immunodeficiency Virus ◽

Cell Surface ◽

Surface Expression ◽

Cell Surface Expression ◽

Coated Pits ◽

Monocytic Cells ◽

Immunodeficiency Virus ◽

Cd4 Cell

ABSTRACT One well-characterized in vitro function of Nef is its ability to remove CD4, the human immunodeficiency virus (HIV) receptor, from the cell surface. Nef accomplishes this by accelerating the internalization and degradation of CD4. Current models propose that Nef promotes CD4 internalization via an increased association of CD4 with clathrin-coated pits (CCP). Here, we investigated the effect of a naturally occurring antiprotozoan antibiotic, ikarugamycin (IKA), on CD4 cell surface expression in human monocytic cells stably expressing HIV type 1 SF2 Nef. IKA was able to efficiently restore CD4 cell surface expression in Nef-expressing cells without affecting either CD4 synthesis or Nef expression. In addition, we demonstrate that IKA is also capable of efficiently blocking CD4 down-modulation in response to phorbol myristate acetate. Our data suggest that IKA may be an efficient and useful inhibitor of CCP-dependent endocytosis.

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