YRRL motifs in the cytoplasmic domain of the thrombopoietin receptor regulate receptor internalization and degradation. 2008

Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
Department of Medicine, University of California San Diego, La Jolla, CA 92093, USA. ihitchcock@ucsd.edu

Thrombopoietin (Tpo), acting through the c-Mpl receptor, promotes the survival and proliferation of hematopoietic stem and progenitor cells and drives megakaryocyte differentiation. The proproliferation and survival signals activated by Tpo must therefore be tightly regulated to prevent uncontrolled cell growth. In this work, we determined the mechanisms that control Tpo-stimulated c-Mpl internalization and defined the processes leading to its degradation. Stimulation of BaF-Mpl cells with Tpo leads to rapid, clathrin-dependent endocytosis of the receptor. Using small interfering RNA (siRNA), we found that inhibition of adaptor protein 2 (AP2), which mediates endocytosis of transmembrane proteins, strongly attenuates Tpo-stimulated c-Mpl internalization. AP2 interacts with YXXPhi motifs and we identified 2 such motifs in c-Mpl (Y(8)RRL and Y(78)RRL) and investigated Tpo-stimulated internalization of receptors bearing point mutations at these sites. After Tpo stimulation, internalization was greatly reduced in c-Mpl Y(78)F and c-Mpl Y(8+78)F, and these cell lines also exhibited increased proliferation and increased strength and duration of Jak2, STAT5, AKT, and ERK1/2 activation in response to Tpo. We also found that the Y(8)RRL motif regulates Tpo-stimulated lysosomal degradation of c-Mpl. Our data establishes that c-Mpl cytoplasmic YRRL motifs are responsible for both Tpo-mediated internalization via interactions with AP2 and lysosomal targeting after endocytosis.

UI MeSH Term Description Entries
D008247 Lysosomes A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured or undergoes MEMBRANE FUSION. (From Rieger et al., Glossary of Genetics: Classical and Molecular, 5th ed). Autolysosome,Autolysosomes,Lysosome
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D002966 Clathrin The main structural coat protein of COATED VESICLES which play a key role in the intracellular transport between membranous organelles. Each molecule of clathrin consists of three light chains (CLATHRIN LIGHT CHAINS) and three heavy chains (CLATHRIN HEAVY CHAINS) that form a structure called a triskelion. Clathrin also interacts with cytoskeletal proteins.
D003593 Cytoplasm The part of a cell that contains the CYTOSOL and small structures excluding the CELL NUCLEUS; MITOCHONDRIA; and large VACUOLES. (Glick, Glossary of Biochemistry and Molecular Biology, 1990) Protoplasm,Cytoplasms,Protoplasms
D004705 Endocytosis Cellular uptake of extracellular materials within membrane-limited vacuoles or microvesicles. ENDOSOMES play a central role in endocytosis. Endocytoses
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000595 Amino Acid Sequence The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION. Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D013926 Thrombopoietin A humoral factor that stimulates the production of thrombocytes (BLOOD PLATELETS). Thrombopoietin stimulates the proliferation of bone marrow MEGAKARYOCYTES and their release of blood platelets. The process is called THROMBOPOIESIS. Megakaryocyte Growth and Development Factor,c-mpl Ligand,MGDF Factor,Megakaryocyte Colony Stimulating Factor,Myeloproliferative Leukemia Virus Oncogene Ligand,Thrombocytopoiesis-Stimulating Factor,Thrombocytopoietin,mpl Ligand,Ligand, c-mpl,Ligand, mpl,Thrombocytopoiesis Stimulating Factor
D053628 Receptors, Thrombopoietin Cell surface receptors that are specific for THROMBOPOIETIN. They contain two central FIBRONECTIN TYPE III DOMAINS and signal through interaction with JANUS KINASES such as JANUS KINASE 2. Antigens, CD110,CD110 Antigens,MPL Ligand Receptor,Thrombopoietin Receptor,Thrombopoietin Receptors
D020816 Amino Acid Motifs Three-dimensional protein structural elements that are composed of a combination of secondary structures. They include HELIX-LOOP-HELIX MOTIFS and ZINC FINGERS. Motifs are typically the most conserved regions of PROTEIN DOMAINS and are critical for domain function. However, the same motif may occur in proteins or enzymes with different functions. AA Motifs,Motifs, Amino Acid,Protein Motifs,Protein Structure, Supersecondary,Supersecondary Protein Structure,AA Motif,Amino Acid Motif,Motif, AA,Motif, Amino Acid,Motif, Protein,Motifs, AA,Motifs, Protein,Protein Motif,Protein Structures, Supersecondary,Supersecondary Protein Structures

Related Publications

Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
July 2003, Blood,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
March 1997, The Journal of biological chemistry,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
October 1994, The Journal of biological chemistry,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
March 1997, Proceedings of the National Academy of Sciences of the United States of America,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
August 2008, The Journal of biological chemistry,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
September 1986, The EMBO journal,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
April 1995, Journal of immunology (Baltimore, Md. : 1950),
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
July 1992, The Journal of biological chemistry,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
January 2009, Cellular immunology,
Ian S Hitchcock, and Maximus M Chen, and Jennifer R King, and Kenneth Kaushansky
February 2002, Experimental hematology,
Copied contents to your clipboard!