scholarly journals Amyloid precursor protein, although partially detergent-insoluble in mouse cerebral cortex, behaves as an atypical lipid raft protein

1999 ◽  
Vol 344 (1) ◽  
pp. 23-30 ◽  
Author(s):  
Edward T. PARKIN ◽  
Anthony J. TURNER ◽  
Nigel M. HOOPER
Keyword(s):  
Alkaline Phosphatase ◽  
Cerebral Cortex ◽  
Lipid Rafts ◽  
Proteolytic Processing ◽  
Low Density ◽  
Marker Proteins ◽  
Mouse Cerebral Cortex ◽  
Aminopeptidase A ◽  
A Minor ◽  
Triton X

Lipid rafts are regions of the plasma membrane that are enriched in cholesterol, glycosphingolipids and acylated proteins, and which have been proposed as sites for the proteolytic processing of the Alzheimer's amyloid precursor protein (APP). Lipid rafts can be isolated on the basis of their insolubility in Triton X-100 at 4 °C, with the resulting low-density, detergent-insoluble glycolipid-enriched fraction (DIG) being isolated by flotation through a sucrose density gradient. The detergent-insolubility of APP in mouse cerebral cortex relative to a variety of DIG marker proteins (alkaline phosphatase, flotillin, F3 protein and prion protein) and non-DIG proteins (alkaline phosphodiesterase I, aminopeptidase A and clathrin) has been examined. Alkaline phosphatase, flotillin, F3 protein and the prion protein were present exclusively in the DIG region of the sucrose gradient over a range of protein/detergent ratios used to solubilize the membranes and displayed a characteristic enrichment in the low-density fraction as the protein/detergent ratio was decreased. In contrast, most of the APP, alkaline phosphodiesterase I, aminopeptidase A and clathrin was effectively solubilized at all of the protein/detergent ratios examined. However, a minor proportion of these latter proteins was detected in DIGs at levels which remained constant irrespective of the protein/detergent ratio. When DIGs were isolated from the sucrose gradients and treated with excess Triton X-100, both the DIG marker proteins and APP, alkaline phosphodiesterase I and clathrin were predominantly resistant to detergent extraction at 37 °C. These results show that, although a minor proportion of APP is present in DIGs, where it is detergent-insoluble even at 37 °C, it behaves as an atypical lipid raft protein and raises questions as to whether lipid rafts are a site for its proteolytic processing.

scholarly journals Association of dengue virus NS1 protein with lipid rafts

2008 ◽  
Vol 89 (10) ◽  
pp. 2492-2500 ◽  
Author(s):  
Sansanee Noisakran ◽  
Thanyaporn Dechtawewat ◽  
Panisadee Avirutnan ◽  
Taroh Kinoshita ◽  
Uamporn Siripanyaphinyo ◽  
...  
Keyword(s):  
Cell Surface ◽  
Dengue Virus ◽  
Lipid Rafts ◽  
Transmembrane Domain ◽  
Gradient Centrifugation ◽  
Ns1 Protein ◽  
Replication Complex ◽  
Infected Cells ◽  
A Minor ◽  
Triton X

During the replication of dengue virus, a viral non-structural glycoprotein, NS1, associates with the membrane on the cell surface and in the RNA replication complex. NS1 lacks a transmembrane domain, and the mechanism by which it associates with the membrane remains unclear. This study aimed to investigate whether membrane-bound NS1 is present in lipid rafts in dengue virus-infected cells. Double immunofluorescence staining of infected HEK-293T cells revealed that NS1 localized with raft-associated molecules, ganglioside GM1 and CD55, on the cell surface. In a flotation gradient centrifugation assay, a small proportion of NS1 in Triton X-100 cell lysate consistently co-fractionated with raft markers. Association of NS1 with lipid rafts was detected for all four dengue serotypes, as well as for Japanese encephalitis virus. Analysis of recombinant NS1 forms showed that glycosylated NS1 dimers stably expressed in HEK-293T cells without an additional C-terminal sequence, or with a heterologous transmembrane domain, failed to associate with lipid rafts. In contrast, glycosylphosphatidylinositol-linked recombinant NS1 exhibited a predilection for lipid rafts. These results indicate an association of a minor subpopulation of NS1 with lipid rafts during dengue virus infection and suggest that modification of NS1, possibly lipidation, is required for raft association.

scholarly journals Detergent-insoluble GPI–anchored Proteins Are Apically Sorted in Fischer Rat Thyroid Cells, but Interference with Cholesterol or Sphingolipids Differentially Affects Detergent Insolubility and Apical Sorting

2000 ◽  
Vol 11 (2) ◽  
pp. 531-542 ◽  
Author(s):  
Concetta Lipardi ◽  
Lucio Nitsch ◽  
Chiara Zurzolo
Keyword(s):  
Alkaline Phosphatase ◽  
Lipid Rafts ◽  
Neurotrophin Receptor ◽  
Apical Surface ◽  
Placental Alkaline Phosphatase ◽  
Thyroid Cells ◽  
Gpi Proteins ◽  
Rat Thyroid ◽  
Apical Sorting ◽  
Triton X

In contrast to Madin–Darby canine kidney cells, Fischer rat thyroid cells deliver the majority of endogenous glycosylphosphatidyl inositol (GPI)–anchored proteins to the basolateral surface. However, we report here that the GPI proteins Placental Alkaline Phosphatase (PLAP) and Neurotrophin Receptor–Placental Alkaline Phosphatase (NTR-PLAP) are apically localized in transfected Fischer rat thyroid cells. In agreement with the “raft hypothesis,” which postulates the incorporation of GPI proteins into glycosphingolipids and cholesterol-enriched rafts, we found that both of these proteins were insoluble in Triton X-100 and floated into the lighter fractions of sucrose density gradients. However, disruption of lipid rafts by removal of cholesterol did not cause surface missorting of PLAP and NTR-PLAP, and the altered surface sorting of these proteins after Fumonisin B1 treatment did not correlate with reduced levels in Triton X-100 –insoluble fractions. Furthermore, in contrast to the GPI-anchored forms of both of these proteins, the secretory and transmembrane forms (in the absence of a basolateral cytoplasmic signal) were sorted to the apical surface without association with lipid microdomains. Together, these data demonstrate that the GPI anchor is required to mediate raft association but is not sufficient to determine apical sorting. They also suggest that signals present in the ectodomain of the proteins play a major role and that lipid rafts may facilitate the recognition of these signals in thetrans-Golgi network, even though they are not required for apical sorting.

scholarly journals BMP signaling alters aquaporin-4 expression in the mouse cerebral cortex

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kazuya Morita ◽  
Naoyuki Matsumoto ◽  
Kengo Saito ◽  
Toshihide Hamabe-Horiike ◽  
Keishi Mizuguchi ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Molecular Mechanisms ◽  
Water Movement ◽  
Water Channel ◽  
Bmp Signaling ◽  
Aquaporin 4 ◽  
Mammalian Brain ◽  
Physiological Conditions ◽  
Pathological Conditions ◽  
Mouse Cerebral Cortex

AbstractAquaporin-4 (AQP4) is a predominant water channel expressed in astrocytes in the mammalian brain. AQP4 is crucial for the regulation of homeostatic water movement across the blood–brain barrier (BBB). Although the molecular mechanisms regulating AQP4 levels in the cerebral cortex under pathological conditions have been intensively investigated, those under normal physiological conditions are not fully understood. Here we demonstrate that AQP4 is selectively expressed in astrocytes in the mouse cerebral cortex during development. BMP signaling was preferentially activated in AQP4-positive astrocytes. Furthermore, activation of BMP signaling by in utero electroporation markedly increased AQP4 levels in the cerebral cortex, and inhibition of BMP signaling strongly suppressed them. These results indicate that BMP signaling alters AQP4 levels in the mouse cerebral cortex during development.

scholarly journals Modeling human‐specific interlaminar astrocytes in the mouse cerebral cortex

2020 ◽  
Vol 529 (4) ◽  
pp. 802-810
Author(s):  
Ragunathan Padmashri ◽  
Baiyan Ren ◽  
Braden Oldham ◽  
Yoosun Jung ◽  
Ryan Gough ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Mouse Cerebral Cortex ◽  
Human Specific
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