Lipid Rafts and Caveolae as Portals for Endocytosis: New Insights and Common Mechanisms

Abstract

Clathrin-coated pits and caveolae are two of the most recognizable features of the plasma membrane of mammalian cells. While our understanding of the machinery regulating and driving clathrin-coated pit-mediated endocytosis has progressed dramatically, including the elucidation of the structure of individual components and partial in vitro reconstitution, the role of caveolae as alternative endocytic carriers still remains elusive 50 years after their discovery. However, recent work has started to provide new insights into endocytosis by caveolae and into apparently related pathways involving lipid raft domains. These pathways, distinguished by their exquisite sensitivity to cholesterol-sequestering agents, can involve caveolae but also exist in cells devoid of caveolins and caveolae. This review examines the current evidence for the involvement of rafts and caveolae in endocytosis and the molecular players involved in their regulation.

Rod‐Shaped Active Drug Particles Enable Efficient and Safe Gene Delivery

“…Nystatin and methyl‐β‐cyclodextrin (M‐CD) are two typical inhibitors for blocking caveolae internalization 15, 19. Therefore, the uptake in cells preincubated with these inhibitors was investigated.…”

“…The uptake of dual‐labeled CNPs in 4T1 cells was decreased by 40% and 30% after the caveolar pathway was suppressed with nystatin or M‐CD ( Figure 2 A), despite the difference in use of fluorescence probes. Caco‐2 cells, in which caveolae constituted 50% cell surface area,19 were further selected to validate the role of the caveolar pathway in CNPs uptake. Again, the uptake of CNPs by Caco‐2 cells declined to ≈52% as caveolae endocytosis was inhibited by nystatin or M‐CD (Figure 2B).…”

Short Ligands Affect Modes of QD Uptake and Elimination in Human Cells

“…The structural and functional role of lipid rafts and caveolin in endocytosis of small molecules was recently discussed, and some common mechanisms were proposed. 48,49 Cysteine, the ligand on the surface of QD-CYS, has a specific transport machinery, the primary sodiumdependent cysteine transporter (X-AG transport system), in both model cell lines selected in this study. Threo-β-hydroxyaspartate (THA), an inhibitor of the X-AG transporter, is a substrate for cysteine, glutamate, and aspartate.…”

Neural cell adhesion molecule (NCAM) marks adult myogenic cells committed to differentiation

“…Table 1 includes 72 of the approximately 250 proteins identified. Many of them are present in or associated with membrane rafts of other cell types [18,26], and/or have been previously described in muscle. Overall, satellite cell DRMs contained primarily signaling intermediates, adhesion and cytoskeletal proteins ( Table 1).…”

“…These regions of the plasma membrane play important roles in intracellular protein transport, membrane fusion and transcytosis; they have also been proposed to act as platforms for assembly of signaling complexes, cell surface antigens and adhesion molecules. Cellular events commonly associated with membrane raft complexes include cell activation, polarization and signaling [17,18]. In other adult stem cells (i.e., hematopoietic stem cells) membrane rafts are critical for cell cycle regulation and survival [19,20], however very little is known about signaling pathways mediated by membrane rafts in satellite cells.…”