Freeze-fracture and immunogold analysis of aquaporin-4 (AQP4) square arrays, with models of AQP4 lattice assembly
| Autor: | C. S. Furman, Kimberly G. V. Davidson, John E. Rash, Thomas Yasumura |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Male
Models Molecular Pathology medicine.medical_specialty Ependymal Cell Macromolecular Substances Aquaporin CHO Cells Biology Aquaporins Article Rats Sprague-Dawley Cerebrospinal fluid Cricetinae Ependyma Parenchyma medicine Animals Freeze Fracturing Protein Isoforms Rats Wistar Aquaporin 4 Glia limitans General Neuroscience Cell Membrane Image Enhancement Immunohistochemistry Rats Molecular Weight Alternative Splicing medicine.anatomical_structure Astrocytes Biophysics Female Choroid plexus sense organs Astrocyte |
| Zdroj: | Neuroscience. 129:915-934 |
| ISSN: | 0306-4522 |
| DOI: | 10.1016/j.neuroscience.2004.06.076 |
| Popis: | Each day, approximately 0.5-0.9 l of water diffuses through (primarily) aquaporin-1 (AQP1) channels in the human choroid plexus, into the cerebrospinal fluid of the brain ventricles and spinal cord central canal, through the ependymal cell lining, and into the parenchyma of the CNS. Additional water is also derived from metabolism of glucose within the CNS parenchyma. To maintain osmotic homeostasis, an equivalent amount of water exits the CNS parenchyma by diffusion into interstitial capillaries and into the subarachnoid space that surrounds the brain and spinal cord. Most of that efflux is through AQP4 water channels concentrated in astrocyte endfeet that surround capillaries and form the glia limitans. This report extends the ultrastructural and immunocytochemical characterizations of the crystalline aggregates of intramembrane proteins that comprise the AQP4 "square arrays" of astrocyte and ependymocyte plasma membranes. We elaborate on recent demonstrations in Chinese hamster ovary cells of the effects on AQP4 array assembly resulting from separate vs. combined expression of M1 and M23 AQP4, which are two alternatively spliced variants of the AQP4 gene. Using improved shadowing methods, we demonstrate sub-molecular cross-bridges that link the constituent intramembrane particles (IMPs) into regular square lattices of AQP4 arrays. We show that the AQP4 core particle is 4.5 nm in diameter, which appears to be too small to accommodate four monomeric proteins in a tetrameric IMP. Several structural models are considered that incorporate freeze-fracture data for submolecular "cross-bridges" linking IMPs into the classical square lattices that characterize, in particular, naturally occurring AQP4. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|
Full Text from ScienceDirect