1
|
Mlinac-Jerkovic K, Kalanj-Bognar S, Heffer M, Blažetić S. Methodological Pitfalls of Investigating Lipid Rafts in the Brain: What Are We Still Missing? Biomolecules 2024; 14:156. [PMID: 38397393 PMCID: PMC10886647 DOI: 10.3390/biom14020156] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2023] [Revised: 01/21/2024] [Accepted: 01/26/2024] [Indexed: 02/25/2024] Open
Abstract
The purpose of this review is to succinctly examine the methodologies used in lipid raft research in the brain and to highlight the drawbacks of some investigative approaches. Lipid rafts are biochemically and biophysically different from the bulk membrane. A specific lipid environment within membrane domains provides a harbor for distinct raftophilic proteins, all of which in concert create a specialized platform orchestrating various cellular processes. Studying lipid rafts has proved to be arduous due to their elusive nature, mobility, and constant dynamic reorganization to meet the cellular needs. Studying neuronal lipid rafts is particularly cumbersome due to the immensely complex regional molecular architecture of the central nervous system. Biochemical fractionation, performed with or without detergents, is still the most widely used method to isolate lipid rafts. However, the differences in solubilization when various detergents are used has exposed a dire need to find more reliable methods to study particular rafts. Biochemical methods need to be complemented with other approaches such as live-cell microscopy, imaging mass spectrometry, and the development of specific non-invasive fluorescent probes to obtain a more complete image of raft dynamics and to study the spatio-temporal expression of rafts in live cells.
Collapse
Affiliation(s)
| | | | - Marija Heffer
- Faculty of Medicine, Josip Juraj Strossmayer University of Osijek, 31000 Osijek, Croatia
| | - Senka Blažetić
- Department of Biology, Josip Juraj Strossmayer University of Osijek, 31000 Osijek, Croatia
| |
Collapse
|
2
|
Start Me Up: How Can Surrounding Gangliosides Affect Sodium-Potassium ATPase Activity and Steer towards Pathological Ion Imbalance in Neurons? Biomedicines 2022; 10:biomedicines10071518. [PMID: 35884824 PMCID: PMC9313118 DOI: 10.3390/biomedicines10071518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/21/2022] [Accepted: 06/24/2022] [Indexed: 12/04/2022] Open
Abstract
Gangliosides, amphiphilic glycosphingolipids, tend to associate laterally with other membrane constituents and undergo extensive interactions with membrane proteins in cis or trans configurations. Studies of human diseases resulting from mutations in the ganglioside biosynthesis pathway and research on transgenic mice with the same mutations implicate gangliosides in the pathogenesis of epilepsy. Gangliosides are reported to affect the activity of the Na+/K+-ATPase, the ubiquitously expressed plasma membrane pump responsible for the stabilization of the resting membrane potential by hyperpolarization, firing up the action potential and ion homeostasis. Impaired Na+/K+-ATPase activity has also been hypothesized to cause seizures by several mechanisms. In this review we present different epileptic phenotypes that are caused by impaired activity of Na+/K+-ATPase or changed membrane ganglioside composition. We further discuss how gangliosides may influence Na+/K+-ATPase activity by acting as lipid sorting machinery providing the optimal stage for Na+/K+-ATPase function. By establishing a distinct lipid environment, together with other membrane lipids, gangliosides possibly modulate Na+/K+-ATPase activity and aid in “starting up” and “turning off” this vital pump. Therefore, structural changes of neuronal membranes caused by altered ganglioside composition can be a contributing factor leading to aberrant Na+/K+-ATPase activity and ion imbalance priming neurons for pathological firing.
Collapse
|
3
|
Ilic K, Lin X, Malci A, Stojanović M, Puljko B, Rožman M, Vukelić Ž, Heffer M, Montag D, Schnaar RL, Kalanj-Bognar S, Herrera-Molina R, Mlinac-Jerkovic K. Plasma Membrane Calcium ATPase-Neuroplastin Complexes Are Selectively Stabilized in GM1-Containing Lipid Rafts. Int J Mol Sci 2021; 22:ijms222413590. [PMID: 34948386 PMCID: PMC8708829 DOI: 10.3390/ijms222413590] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2021] [Revised: 12/03/2021] [Accepted: 12/14/2021] [Indexed: 12/20/2022] Open
Abstract
The recent identification of plasma membrane (Ca2+)-ATPase (PMCA)-Neuroplastin (Np) complexes has renewed attention on cell regulation of cytosolic calcium extrusion, which is of particular relevance in neurons. Here, we tested the hypothesis that PMCA-Neuroplastin complexes exist in specific ganglioside-containing rafts, which could affect calcium homeostasis. We analyzed the abundance of all four PMCA paralogs (PMCA1-4) and Neuroplastin isoforms (Np65 and Np55) in lipid rafts and bulk membrane fractions from GM2/GD2 synthase-deficient mouse brains. In these fractions, we found altered distribution of Np65/Np55 and selected PMCA isoforms, namely PMCA1 and 2. Cell surface staining and confocal microscopy identified GM1 as the main complex ganglioside co-localizing with Neuroplastin in cultured hippocampal neurons. Furthermore, blocking GM1 with a specific antibody resulted in delayed calcium restoration of electrically evoked calcium transients in the soma of hippocampal neurons. The content and composition of all ganglioside species were unchanged in Neuroplastin-deficient mouse brains. Therefore, we conclude that altered composition or disorganization of ganglioside-containing rafts results in changed regulation of calcium signals in neurons. We propose that GM1 could be a key sphingolipid for ensuring proper location of the PMCA-Neuroplastin complexes into rafts in order to participate in the regulation of neuronal calcium homeostasis.
Collapse
Affiliation(s)
- Katarina Ilic
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia; (K.I.); (M.S.); (B.P.); (S.K.-B.)
- BRAIN Centre, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience (IOPPN), King’s College London, London SE5 9NU, UK
| | - Xiao Lin
- Neurogenetics Laboratory, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany; (X.L.); (D.M.)
- Synaptic Signalling Laboratory, Combinatorial NeuroImaging, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany; (A.M.); (R.H.-M.)
| | - Ayse Malci
- Synaptic Signalling Laboratory, Combinatorial NeuroImaging, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany; (A.M.); (R.H.-M.)
| | - Mario Stojanović
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia; (K.I.); (M.S.); (B.P.); (S.K.-B.)
- Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
| | - Borna Puljko
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia; (K.I.); (M.S.); (B.P.); (S.K.-B.)
- Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
| | - Marko Rožman
- Department of Physical Chemistry, Ruđer Bošković Institute, 10000 Zagreb, Croatia;
| | - Željka Vukelić
- Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
| | - Marija Heffer
- Department of Medical Biology and Genetics, Faculty of Medicine, University of Osijek, 31000 Osijek, Croatia;
| | - Dirk Montag
- Neurogenetics Laboratory, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany; (X.L.); (D.M.)
| | - Ronald L. Schnaar
- Departments of Pharmacology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA;
| | - Svjetlana Kalanj-Bognar
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia; (K.I.); (M.S.); (B.P.); (S.K.-B.)
- Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
| | - Rodrigo Herrera-Molina
- Synaptic Signalling Laboratory, Combinatorial NeuroImaging, Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany; (A.M.); (R.H.-M.)
- Centro Integrativo de Biología y Química Aplicada, Universidad Bernardo O’Higgins, Santiago 8307993, Chile
- Center for Behavioral Brain Sciences, 39120 Magdeburg, Germany
| | - Kristina Mlinac-Jerkovic
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia; (K.I.); (M.S.); (B.P.); (S.K.-B.)
- Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, 10000 Zagreb, Croatia;
- Correspondence:
| |
Collapse
|
4
|
Mlinac-Jerkovic K, Ilic K, Zjalić M, Mandić D, Debeljak Ž, Balog M, Damjanović V, Maček Hrvat N, Habek N, Kalanj-Bognar S, Schnaar RL, Heffer M. Who's in, who's out? Re-evaluation of lipid raft residents. J Neurochem 2021; 158:657-672. [PMID: 34081780 PMCID: PMC8363533 DOI: 10.1111/jnc.15446] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 05/19/2021] [Accepted: 05/19/2021] [Indexed: 01/01/2023]
Abstract
Lipid rafts, membrane microdomains enriched with (glyco)sphingolipids, cholesterol, and select proteins, act as cellular signalosomes. Various methods have been used to separate lipid rafts from bulk (non‐raft) membranes, but most often, non‐ionic detergent Triton X‐100 has been used in their isolation. However, Triton X‐100 is a reported disruptor of lipid rafts. Histological evidence confirmed raft disruption by Triton X‐100, but remarkably revealed raft stability to treatment with a related polyethylene oxide detergent, Brij O20. We report isolation of detergent‐resistant membranes from mouse brain using Brij O20 and its use to determine the distribution of major mammalian brain gangliosides, GM1, GD1a, GD1b and GT1b. A different distribution of gangliosides—classically used as a raft marker—was discovered using Brij O20 versus Triton X‐100. Immunohistochemistry and imaging mass spectrometry confirm the results. Use of Brij O20 results in a distinctive membrane distribution of gangliosides that is not all lipid raft associated, but depends on the ganglioside structure. This is the first report of a significant proportion of gangliosides outside raft domains. We also determined the distribution of proteins functionally related to neuroplasticity and known to be affected by ganglioside environment, glutamate receptor subunit 2, amyloid precursor protein and neuroplastin and report the lipid raft populations of these proteins in mouse brain tissue. This work will enable more accurate lipid raft analysis with respect to glycosphingolipid and membrane protein composition and lead to improved resolution of lipid–protein interactions within biological membranes.
Collapse
Affiliation(s)
- Kristina Mlinac-Jerkovic
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Katarina Ilic
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Milorad Zjalić
- Department of Medical Biology and Genetics, Faculty of Medicine, University of Osijek, Osijek, Croatia
| | - Dario Mandić
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, Osijek, Croatia.,Department of Medical Chemistry, Biochemistry and Clinical Chemistry, Faculty of Medicine, University of Osijek, Osijek, Croatia
| | - Željko Debeljak
- Clinical Institute of Laboratory Diagnostics, Osijek University Hospital, Osijek, Croatia.,Department of Pharmacology, Faculty of Medicine, University of Osijek, Osijek, Croatia
| | - Marta Balog
- Department of Medical Biology and Genetics, Faculty of Medicine, University of Osijek, Osijek, Croatia
| | - Vladimir Damjanović
- Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Nikolina Maček Hrvat
- Biochemistry and Organic Analytical Chemistry Unit, Institute for Medical Research and Occupational Health, Zagreb, Croatia
| | - Nikola Habek
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Svjetlana Kalanj-Bognar
- Croatian Institute for Brain Research, School of Medicine, University of Zagreb, Zagreb, Croatia.,Department of Chemistry and Biochemistry, School of Medicine, University of Zagreb, Zagreb, Croatia
| | - Ronald L Schnaar
- Departments of Pharmacology and Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Marija Heffer
- Department of Medical Biology and Genetics, Faculty of Medicine, University of Osijek, Osijek, Croatia
| |
Collapse
|