SHARPIN is an endogenous inhibitor of beta 1-integrin activation

Regulated activation of integrins is critical for cell adhesion, motility and tissue homeostasis. Talin and kindlins activate beta 1-integrins, but the counteracting inhibiting mechanisms are poorly defined. We identified SHARPIN as an important inactivator of beta 1-integrins in an RNAi screen. SHARPIN inhibited beta 1-integrin functions in human cancer cells and primary leukocytes. Fibroblasts, leukocytes and keratinocytes from SHARPIN-deficient mice exhibited increased beta 1-integrin activity, which was fully rescued by re-expression of SHARPIN. We found that SHARPIN directly binds to a conserved cytoplasmic region of integrin alpha-subunits and inhibits recruitment of talin and kindlin to the integrin. Therefore, SHARPIN inhibits the critical switching of beta 1-integrins from inactive to active conformations

Cargo-specific recruitment in clathrin and dynamin-independent endocytosis

Spatially controlled, cargo-specific endocytosis is essential for development, tissue homeostasis, and cancer invasion and is often hijacked by viral infections. Unlike clathrin-mediated endocytosis, which exploits cargo-specific adaptors for selective protein internalization, the clathrin and dynamin-independent endocytic pathway (CLIC-GEEC, CG-pathway) has until now been considered a bulk internalization route for the fluid phase, glycosylated membrane proteins and lipids. Although the core molecular players of CG endocytosis have been recently defined, no cargo-specific adaptors are known and evidence of selective protein uptake into the pathway is lacking. Here, we identify the first cargo-specific adaptor for CG-endocytosis and demonstrate its clinical relevance in breast cancer progression. By combining unbiased molecular characterization and super-resolution imaging, we identified the actin-binding protein swiprosin-1 (EFHD2) as a cargo-specific adaptor regulating integrin internalization via the CG-pathway. Swiprosin-1 couples active Rab21-associated integrins with key components of the CG-endocytic machinery, IRSp53 and actin. Swiprosin-1 is critical for integrin endocytosis, but not for other CG-cargo and supports integrin-dependent cancer cell migration and invasion, with clinically relevant implications for breast cancer. Our results demonstrate a previously unknown cargo selectivity for the CG-pathway and opens the possibility to discover more adaptors regulating it

Debrecen-Nagyváradi Értesítő

A Debreczen-Nagyváradi Értesítő 1843. jún. 13.-1902. aug. között hetenként, később havonként megjelenő, hirdető, szépirodalmi és vegyes tartalmú közérdekű hírlap

Crystal Structure of the Human Retinitis Pigmentosa 2 Protein and Its Interaction with Arl3

Crystal Structure of the Human Retinitis Pigmentosa 2 Protein and Its Interaction with Arl

ENDOCYTOSIS OF HUMAN-IGG - FC RECEPTOR COMPLEXES BY TRANSFECTED BHK CELLS

HONING S, JOCKUSCH BM, KREIMER G, et al. ENDOCYTOSIS OF HUMAN-IGG - FC RECEPTOR COMPLEXES BY TRANSFECTED BHK CELLS. EUROPEAN JOURNAL OF CELL BIOLOGY. 1991;55(1):48-59.We have analyzed the mode of uptake of human beta-FcRII molecules expressed in BHK cells (clone 2/14). When challenged with aggregated human IgG (ahIgG), these cells bind the ligand at 4-degrees-C and endocytose the IgG:receptor complexes rapidly upon warming to 37-degrees-C, as seen by fluorescence microscopy with antibodies directed against human IgG. Using I-125-labeled ahIgG, we found that 40% of the bound ligand was internalized within 15 min, and approximately 60% within 2 h. Surface replication and thin sectioning combined with immunogold labeling revealed that the ligand was taken up by coated vesicles and was transferred to the endosomal/lysosomal compartment. This was confirmed by confocal laser microscopy of cells double labeled for clathrin and ahIgG. After modulation of the coated vesicle pattern by hypertonic medium, ahIgG transport was impaired. These data show that a single isoform of human FcRII, expressed in an animal cell negative for Fc receptors, can use the coated vesicle based endocytic pathway of the host cell. Reincubation of cycloheximide-treated cells with a second batch of ligand showed that approximately 20% of the beta-FcRII was recycled. This finding is in apparent contrast to the fate of the endogenous Fc receptors expressed on mouse macrophages