Human neutrophils are devoid of the integral membrane protein caveolin

Abstract

The secretory vesicles of human neutrophils are rapidly mobilizable vesicles that contain several GPI-linked proteins, a characteristic feature of caveolae in other cells. To investigate whether secretory vesicles are structurally related to caveolae, we examined human neutrophils for the presence of caveolin, a major constituent of caveolae, by immunoblotting using monoclonal and polyclonal antibodies. Caveolin was not detected in lysates of human neutrophils nor in isolated plasma membrane/light membrane fractions in which secretory vesicles localize. In contrast, caveolin was readily detected in isolated membranes of adipose cells. We conclude that human neutrophils are devoid of caveolin and that secretory vesicles are not related to caveolae nor dependent on caveolae for mobilization.

Expression and Characterization of Glycolipid-Anchored B7-1 (CD80) from Baculovirus-Infected Insect Cells: Protein Transfer onto Tumor Cells

“…Earlier studies from our laboratory have demonstrated that GPI-anchored CD16B expressed on neutrophils can be completely solubilized using Triton X-100 at 4°C (14). It has been reported that neutrophils do not express caveolin (42). Therefore, caveolin or MAL proteolipid-like proteins may not be expressed in insect cells.…”

Amantadine inhibits platelet-activating factor induced clathrin-mediated endocytosis in human neutrophils

“…to clathrin-coated pits (19). This ends the initial stage of receptor signaling; however, sequestering receptors to clathrin-coated pits induces recruitment of endocytotic machinery and signaling complexes to the membrane (4,15,19,34,56,64). Such signaling cascades post receptor-ligand binding have been implicated as potential platforms for staging the assembly of signaling complexes that can be trafficked to various intracellular destinations (23,62).…”

“…Recent work has characterized the early events in PAF-mediated CME (25) including internalization of the ligand:receptor complex and sequestration of these ligated receptors to clathrin-coated vesicle (CCVs) (55). In addition, the PMN is unique for it does not contain caveolin and thus serves as an excellent cellular model to study CME (56). Therefore, we hypothesize that amantadine inhibits CME, which is required for PAF signaling and for PAF-mediated changes in PMN physiology.…”

Membrane lipid microdomains differentially regulate intracellular signaling events in human neutrophils

“…One hypothesis is that lipid rafts may represent precursors of caveolae that facilitate the insertion of caveolins into membranes [15]. However, human neutrophils seem to be devoid of caveolins [24] but the lipid microdomains are still identifiable in their plasma membranes [25], suggesting that lipid rafts may play well-defined physiological roles in the absence of caveolins. This view is supported by several reports [25 -27] showing that cholesterol depletion from the plasma membrane prevents isolation of lipid raft by centrifugation on sucrose gradients and at the same time selectively interferes with certain intracellular signaling events such as cytosolic free calcium increase [28] or phosphorylation of Src-family tyrosine kinases [25 -27].…”