Pathways and itinerary of clathrin-independent endocytosis

不依赖网格蛋白的内吞作用的途径和行程

• 批准号: 8746636
• 负责人: Julie G Donaldson
• 金额: $ 5.63万
• 依托单位: NATIONAL HEART, LUNG, AND BLOOD INSTITUTE
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8746636
• 关键词: Acidic Amino Acids; Amino Acid Sequence; Antigens; Back; CD44 gene; Cell Surface Proteins; Cell membrane; Cell physiology; Cell surface; Cell-Cell Adhesion; Cells; Clathrin; Cytoplasmic Tail; Endocytosis; Endosomes; Immune system; Label; Laboratories; Life; Link; Lysosomes; Major Histocompatibility Complex; Membrane; Membrane Proteins; Microtubules; Neoplasm Metastasis; Nutrient; Pathway interactions; Process; Proteins; Recycling; Regulation; Route; Sorting - Cell Movement; Transferrin Receptor; Travel; Tube; Work; cancer cell; cell motility; interest; late endosome; receptor; trafficking; uptake

This project is focused on understanding clathrin-independent forms of endocytosis. Endocytosis that occurs without clathrin coats occurs in all cells but is poorly understood. We are interested in studying the cargo proteins that enter cells by this mechanism, their intracellular itinerary once they have been internalized and whether they contain amino acid sequences that allow for specialized sorting within cells. We have been identifying new cargo proteins and found that a subset of these proteins take alternative traffic routes once they have entered cells. The major histocompatibility complex Class I protein (MHCI), is a prototypical clathrin-indepenent cargo protein and after internalization it reaches endosomes that contain cargo proteins such as the transferrin receptor that enter via clathrin-depenent endocytosis. From there, MHCI travels either to late endosomes and lysosomes where it is degraded or on to recycling tubules that return MHCI back to the cell surface. CD44, CD98, and CD147, however, show an altered itinerary in many cells where they traffic directly into the recycling tubules and avoid trafficking to late endosomal compartments. Consistent with this altered itinerary, CD44, CD98 and CD147 are long-lived proteins and are not degraded like MHCI, which is routed to late endosomes. We have now identified (Maldonado-Baez et al, 2013) sequences in the cytoplasmic domain of CD98 and CD147 that allow these cargo proteins to avoid trafficking to endosomes labeled with the early endosomal antigen 1 (EEA1) and lysosomes but instead traffic to recycling tubules. These sequences are transferrable and include di-acidic amino acid residues. We identified the microtubule and cargo tethering protein Hook1 as interacting with the cytoplasmic tails of CD98 and CD147 and responsible for this sorting function. In addition, we found that Hook1 works together with Rab22a and microtubules to sort CD98 and CD147 into recycling tubules. We are currently investigating other aspects of this sorting machine, such as identifying other components that link cargo sorting to tube formation and facilitation of recycling.

该项目的重点是了解网格蛋白独立形式的内吞作用。 在没有网格蛋白外壳的情况下发生的内吞作用发生在所有细胞中，但人们对此知之甚少。 我们感兴趣的是研究通过这种机制进入细胞的货物蛋白、它们被内化后的细胞内行程以及它们是否含有允许在细胞内进行专门分类的氨基酸序列。 我们一直在鉴定新的货物蛋白，并发现这些蛋白的一部分一旦进入细胞就会采取替代的运输路线。 主要组织相容性复合物 I 类蛋白 (MHCI) 是一种典型的不依赖于网格蛋白的货物蛋白，在内化后，它到达含有货物蛋白的内涵体，例如通过网格蛋白依赖性内吞作用进入的转铁蛋白受体。 从那里，MHCI 要么进入晚期内体和溶酶体，在那里被降解，要么进入回收小管，将 MHCI 返回到细胞表面。然而，CD44、CD98 和 CD147 在许多细胞中表现出改变的行程，它们直接进入循环小管，并避免运输到晚期内体区室。 与这种改变的行程一致，CD44、CD98和CD147是长寿命蛋白质，不会像MHCI那样被降解，MHCI会被路由到晚期内体。 我们现在已经鉴定了（Maldonado-Baez 等人，2013）CD98 和 CD147 胞质结构域中的序列，这些序列允许这些货物蛋白避免运输到标记有早期内体抗原 1 (EEA1) 和溶酶体的内体，而是运输到回收小管。 这些序列是可转移的并且包括二酸性氨基酸残基。 我们鉴定出微管和货物束缚蛋白 Hook1 与 CD98 和 CD147 的细胞质尾部相互作用，并负责这种分选功能。 此外，我们发现Hook1与Rab22a和微管一起将CD98和CD147分选到回收小管中。 我们目前正在研究该分拣机的其他方面，例如确定将货物分拣与管道形成和促进回收联系起来的其他组件。