Original Article
Autoimmunoreactive IgGs against cardiac lipid raft-associated proteins in patients with postural orthostatic tachycardia syndrome

https://doi.org/10.1016/j.trsl.2013.03.002Get rights and content

Lipid rafts are specialized plasma membrane microdomains that serve as platforms for integrating cellular signal transductions. We have recently reported that autoantibodies against cardiac membrane proteins are present in patients with postural orthostatic tachycardia syndrome (POTS). In this study, we examined the presence of autoimmunoreactive IgGs against lipid raft proteins in these patients. IgGs were purified from the sera of 10 patients and 7 normal controls. Cardiac lipid raft preparations were isolated from normal human heart tissue. The lipid raft-associated proteins were resolved by 2-dimensional gel electrophoresis and immunoblotted against IgGs from each subject. Protein spots that reacted specifically with patient IgGs were identified by nano-liquid chromatography-mass spectrometry/mass spectrometry. Thirty-four such protein spots, and 72 unique proteins were identified. The targets of autoimmunoreactive IgGs include proteins associated with caveolae structure, adrenergic signaling, calcium signaling, cytostructures, chaperone and energy metabolism. Multiple pathways were involved including those that regulate caveolae-mediated signaling, oxidative phosphorylation, fatty acid metabolism, protein ubiquitination, and cardiac β-adrenergic signaling. Our results suggest that cardiac lipid raft-associated proteins are targets of autoimmunoreactive IgGs from patients with POTS. Autoimmunity may play a role in the pathogenesis of POTS.

Section snippets

Study subjects and IgG isolation

This study was approved by the Mayo Clinic Institutional Review Board, and all participants provided written informed consent. Patients were excluded if they had a history of confirmed autoimmune diseases. Seven control subjects (6 females and 1 male, average age 36.1 years) and 10 patients with the diagnosis of POTS (7 females and 3 males, average age 35.1 years) provided 30 mL of venous blood. The detailed clinical and laboratory profiles of the subjects and controls are outlined in Table I.

Results

We first evaluated the effectiveness of lipid raft/caveolae-rich fraction isolation. Caveolin-3, the marker of cardiomyocyte caveolae, was enriched in the low buoyant density fractions (Fig 1). In contrast, the nonlipid raft membrane marker, clathrin, and the subcellular organelle marker Golgi 58, were differentially distributed (Fig 1). Clathrin appeared predominantly in the heavier fractions of the gradient, suggesting the exclusion of clathrin-coated pits as well as clathrin-associated

Discussion

In this pilot study, we have made the following observations. First, autoantibodies against cardiac lipid raft microdomain proteins are present in patients with POTS. Second, multiple lipid raft/caveolae proteins are potential targets of the autoantibodies in POTS. Third, the presence of autoantibodies may affect the regulation of multiple cellular processes in patients with POTS.

Proteomic technologies have provided ideal tools in the search of antigens and antibodies in autoimmune diseases.

References (32)

  • R.G. Parton et al.

    The multiple faces of caveolae

    Nat Rev Mol Cell Biol

    (2007)
  • M. Bucci et al.

    In vivo delivery of the caveolin-1 scaffolding domain inhibits nitric oxide synthesis and reduces inflammation

    Nat Med

    (2000)
  • J. Yu et al.

    Direct evidence for the role of caveolin-1 and caveolae in mechanotransduction and remodeling of blood vessels

    J Clin Invest

    (2006)
  • P.G. Frank et al.

    Role of caveolin-1 in the regulation of lipoprotein metabolism

    Am J Physiol

    (2008)
  • P.G. Frank et al.

    Caveolin-1 and regulation of cellular cholesterol homeostasis

    Am J Physiol Heart Circ Physiol

    (2006)
  • L.M. Davies et al.

    Interaction with caveolin-1 modulates vascular ATP-sensitive potassium (KATP) channel activity

    J Physiol

    (2010)
  • Cited by (30)

    • Postural orthostatic tachycardia syndrome: New concepts in pathophysiology and management

      2023, Trends in Cardiovascular Medicine
      Citation Excerpt :

      Later in 2000, Verino et al. found evidence of autoantibodies to ganglionic acetylcholine receptors in autoimmune autonomic neuropathies [17]. Years later in 2013, Wang et al. found auto-immunoreactive IgGs against cardiac lipid-raft associated proteins in POTS patients [18]. In 2014, Li et al. found adrenergic receptor antibodies in POTS patients first suggesting a potential alpha adrenergic mechanism for an autoimmune pathogenesis [19].

    • Postural Orthostatic Tachycardia Syndrome (POTS): An Update for Clinical Practice

      2022, Current Problems in Cardiology
      Citation Excerpt :

      These autoantibodies target the G-protein coupled receptors facilitating vasoconstriction through a1-adrenergic receptors and subsequent tachycardia through b-adrenergic receptors activation.28 Wang et al. were the first group to report the autoantibodies against cardiac proteins, including those against cardiac lipid-raft-specific proteins providing an insight into the role of cardiac dysautonomia in POTS.26,29 Another group of autoantibodies against angiotensin II type 1 receptor (AT1R) investigated by Yu et al. were suspected to impair vascular response and alter postural homeostasis function, either separately or by interacting with a1-adrenergic receptors.22

    • Postural orthostatic tachycardia syndrome (POTS): State of the science and clinical care from a 2019 National Institutes of Health Expert Consensus Meeting - Part 1

      2021, Autonomic Neuroscience: Basic and Clinical
      Citation Excerpt :

      Positive (though often non-specific) autoantibody tests are frequently seen among POTS patients, and about 20% report a history of an autoimmune disorder such as Hashimoto's thyroiditis, rheumatoid arthritis or Sjögren syndrome (Blitshteyn, 2015; Shaw et al., 2019). In recent years, a focus of POTS research has been on autoantibodies to cardiovascular G-protein coupled membrane receptors (see below) (Blitshteyn, 2015; Dahan et al., 2016; Fedorowski et al., 2017; Gunning et al., 2019; Li et al., 2014; Ruzieh et al., 2017a; Schofield and Chemali, 2019; Vernino and Stiles, 2018; Wang et al., 2013; Watari et al., 2018; Xichun et al., 2020). Other proposed pathophysiological mechanisms include abnormally increased sympathetic activity and circulating catecholamine excess (“hyperadrenergic POTS”) (Jacob and Biaggioni, 1999; Schondorf and Low, 1993), peripheral sympathetic noradrenergic denervation leading to venous pooling and relative central hypovolemia (“neuropathic POTS”) (Istvan and Roy, 2004; Jacob et al., 2000; Peltier et al., 2010), and low blood volume (absolute hypovolemia).

    • Clinical neurophysiology of postural tachycardia syndrome

      2019, Handbook of Clinical Neurology
      Citation Excerpt :

      The cause of the restricted autonomic neuropathy is often not identified, though approximately one-half of patients report an antecedent illness of presumed viral etiology (Schondorf and Low, 1993; Low et al., 1994; Thieben et al., 2007). The presence of organ-specific autoantibodies in up to one-third of patients (against thyroid antigens more often than the α3 subunit of the ganglionic nicotinic acetylcholine receptor or other targets) further suggests an autoimmune cause in at least some patients with neuropathic POTS (Thieben et al., 2007; Wang et al., 2013; Li et al., 2014; Singer et al., 2015). Gastrointestinal complaints such as bloating, nausea, constipation, and abdominal pain are reported to be more frequent in POTS with peripheral denervation (Al-Shekhlee et al., 2005), though this does not necessarily implicate a widespread cholinergic neuropathy affecting the gastrointestinal tract.

    • Autoimmunity in postural orthostatic tachycardia syndrome: Current understanding

      2018, Autonomic Neuroscience: Basic and Clinical
      Citation Excerpt :

      Forty unique protein antigens were identified using a proteomics approach. In a follow-up study, this group used sera from a small POTS cohort (10 patients) to identify antibodies binding to cardiac lipid rafts (a membrane subfraction) (Wang et al., 2013). Again a large number of potential antigens were identified (over 70) with no consistent pattern of antibody specificity.

    View all citing articles on Scopus

    This work was supported by grants from the National Institutes of Health HL74180 and HL080118 (to H.L.), and the Mayo Clinic Foundation (to W.K.S). All authors have declared no potential conflict of interest, and have read the policy on disclosure of potential conflicts of interest.

    Xiao-Li Wang and Tian-You Ling contributed equally to this work.

    View full text