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J Biol Chem. 2012 Apr 20; FGF21 stimulates FGFR1c activity in cells that co-express Klothoβ (KLB); however, relatively little is known about the interaction of these receptors at the plasma membrane. We measured the dynamics and distribution of fluorescent protein-tagged KLB and FGFR1c in living cells using fluorescence recovery after photobleaching (FRAP) and Number and Brightness (N&B) analysis. We confirmed fluorescent protein-tagged KLB translocates to the plasma membrane and is active when co-expressed with FGFR1c. FGF21-induced signaling was enhanced in cells treated with lactose, a competitive inhibitor of the galectin lattice, suggesting lattice-binding modulates KLB and/or FGFR1c activity. FRAP analysis consistently revealed that lactose treatment increased KLB mobility at the plasma membrane, but did not affect the mobility of FGFR1c. The association of endogenous KLB with the galectin lattice was also confirmed by co-immunoprecipitation with galectin-3. KLB mobility increased when co-expressed with FGFR1c suggesting the two receptors form a hetero-complex independent of the galectin lattice. N&B analysis revealed that KLB and FGFR1c behave as monomers and dimers at the plasma membrane, respectively. Co-expression resulted in monomeric expression of KLB and FGFR1c consistent with formation of a 1:1 hetero-complex. Subsequent addition of FGF21 induced FGFR1 dimerization without changing KLB aggregate size suggesting formation of a 1:2 KLB:FGFR1c signaling complex. Overall, these data suggest KLB and FGFR1 form a 1:1 hetero-complex independent of the galectin lattice that transitions to a 1:2 complex upon addition of FGF21.
J Biol Chem. 2012 Apr 20; FGF21 stimulates FGFR1c activity in cells that co-express Klothoβ (KLB); however, relatively little is known about the interaction of these receptors at the plasma membrane. We measured the dynamics and distribution of fluorescent protein-tagged KLB and FGFR1c in living cells using fluorescence recovery after photobleaching (FRAP) and Number and Brightness (N&B) analysis. We confirmed fluorescent protein-tagged KLB translocates to the plasma membrane and is active when co-expressed with FGFR1c. FGF21-induced signaling was enhanced in cells treated with lactose, a competitive inhibitor of the galectin lattice, suggesting lattice-binding modulates KLB and/or FGFR1c activity. FRAP analysis consistently revealed that lactose treatment increased KLB mobility at the plasma membrane, but did not affect the mobility of FGFR1c. The association of endogenous KLB with the galectin lattice was also confirmed by co-immunoprecipitation with galectin-3. KLB mobility increased when co-expressed with FGFR1c suggesting the two receptors form a hetero-complex independent of the galectin lattice. N&B analysis revealed that KLB and FGFR1c behave as monomers and dimers at the plasma membrane, respectively. Co-expression resulted in monomeric expression of KLB and FGFR1c consistent with formation of a 1:1 hetero-complex. Subsequent addition of FGF21 induced FGFR1 dimerization without changing KLB aggregate size suggesting formation of a 1:2 KLB:FGFR1c signaling complex. Overall, these data suggest KLB and FGFR1 form a 1:1 hetero-complex independent of the galectin lattice that transitions to a 1:2 complex upon addition of FGF21. Int J Mol Med . 2012 Apr 10; Lin CC, Chou CH, Lin TC, Yang MC, Cho CL, Chang CH, Yu HS, Lai CH, Chen LK, Hong YR Orientia tsutsugamushi (O. tsutsugamushi), the causative agent of scrub typhus, is an obligate intracellular pathogen. Recent studies have demonstrated the complete genome of O. tsutsugamushi. Int J Mol Med . 2012 Apr 10; Lin CC, Chou CH, Lin TC, Yang MC, Cho CL, Chang CH, Yu HS, Lai CH, Chen LK, Hong YR Orientia tsutsugamushi (O. tsutsugamushi), the causative agent of scrub typhus, is an obligate intracellular pathogen. Recent studies have demonstrated the complete genome of O. tsutsugamushi.
PLoS One. 2012; 7(4): e33042 Plasma membranes in eukaryotic cells display asymmetric lipid distributions with aminophospholipids concentrated in the inner leaflet and sphingolipids in the outer leaflet. This unequal distribution of lipids between leaflets is, amongst several proposed functions, hypothesized to be a prerequisite for endocytosis. P4 ATPases, belonging to the P-type ATPase superfamily of pumps, are involved in establishing lipid asymmetry across plasma membranes, but P4 ATPases have not been identified in plant plasma membranes. Here we report that the plant P4 ATPase ALA1, which previously has been connected with cold tolerance of Arabidopsis thaliana, is targeted to the plasma membrane and does so following association in the endoplasmic reticulum with an ALIS protein β-subunit. Go here to read the rest:
PLoS One. 2012; 7(4): e33042 Plasma membranes in eukaryotic cells display asymmetric lipid distributions with aminophospholipids concentrated in the inner leaflet and sphingolipids in the outer leaflet. This unequal distribution of lipids between leaflets is, amongst several proposed functions, hypothesized to be a prerequisite for endocytosis. P4 ATPases, belonging to the P-type ATPase superfamily of pumps, are involved in establishing lipid asymmetry across plasma membranes, but P4 ATPases have not been identified in plant plasma membranes. Here we report that the plant P4 ATPase ALA1, which previously has been connected with cold tolerance of Arabidopsis thaliana, is targeted to the plasma membrane and does so following association in the endoplasmic reticulum with an ALIS protein β-subunit. View original post here:
J Biol Chem. 2012 Apr 19; The Rho family of small GTPases are membrane-associated molecular switches involved in the control of a wide range of cellular activities, including cell migration, adhesion, and proliferation. Cdc42 GTPase-activating protein (CdGAP) is a phosphoprotein showing GAP activity towards Rac1 and Cdc42. CdGAP activity is regulated in an adhesion-dependent manner and more recently, we have identified CdGAP as a novel molecular target in signaling and an essential component in the synergistic interaction between TGFβ and Neu/ErbB-2 signaling pathways in breast cancer cells. In this study, we identified a small polybasic region (PBR) preceding the RhoGAP domain that mediates specific binding to negatively charged phosphatidylinositol-3,4,5 trisphosphate (PI(3,4,5)P3). In vitro reconstitution of membrane vesicles loaded with prenylated Rac1 demonstrates that the PBR is required for full activation of CdGAP in the presence of PI(3,4,5)P3. In fibroblast cells, the expression of CdGAP protein mutants lacking an intact PBR shows a significant reduced ability of the protein mutants to induce cell rounding or to mediate negative effects on cell spreading. Furthermore, an intact PBR is required for CdGAP to inactivate Rac1 signaling into cells whereas it is not essential in an in vitro context. Altogether, these studies reveal that specific interaction between negatively charged phospholipid PI(3,4,5)P3 and the stretch of polybasic residues preceding the RhoGAP domain regulates CdGAP activity in vivo and is required for its cellular functions. PLoS One . 2012; 7(4): e33073 Smani Y, McConnell MJ, Pachón J Adhesion to host cells is an initial and important step in Acinetobacter baumannii pathogenesis. However, there is relatively little information on the mechanisms by which A. See the rest here: Cancer Res . 2012 Apr 16; Earley S, Vinegoni C, Dunham J, Gorbatov R, Fumene Feruglio P, Weissleder R Observing drug responses in the tumor microenvironment in vivo can be technically challenging. As a result, cellular responses to molecularly targeted cancer drugs are often studied in cell culture, which does not accurately represent the behavior of cancer cells growing in vivo. Go here to see the original: |
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