TY - JOUR
T1 - The lymphoma transmembrane glycoprotein GP85 (CD44) is a novel guanine nucleotide-binding protein which regulates GP85 (CD44)-ankyrin interaction
AU - Lokeshwar, Vinata B.
AU - Bourguignon, Lilly Y.W.
N1 - Copyright:
Copyright 2004 Elsevier B.V., All rights reserved.
PY - 1992/11/5
Y1 - 1992/11/5
N2 - In this study, we have used photoaffinity labeling by [32P]azido-GTP as well as [32P]ADP-ribosylation by pertussis toxin (PT) and cholera toxin (CT) to identify GTP-binding proteins associated with mouse T-lymphoma plasma membranes. Our results indicate that GP85 (CD44) can be photoaffinity labeled by [32P] azido-GTP and [32P]ADP-ribosylated by both PT and CT. Using purified GP85 (CD44) obtained by Triton X-100 extraction, wheat germ agglutinin-Sepharose, and anti-GP85 (CD44) antibody affinity chromatographies, we have further characterized GP85 (CD44) as a GTP-binding protein. GP85 (CD44) is found to bind guanosine 5′-3-O-(thio)triphosphate (GTPγS) in a time- and dose-dependent manner with a dissociation constant of 0.83 nM. Importantly, GP85 (CD44) appears to display a GTPase activity which hydrolyzes [γ-32P]GTP at a rate of 0.011 mol of Pi released/mol of GP85 (CD44)/min. This GTPase activity can be readily inhibited by PT- or CT-mediated ribosylation of GP85 (CD44). Most interestingly, GTP binding significantly enhances the interaction of purified GP85 (CD44) with ankyrin, whereas ADP-ribosylation of GP85 (CD44) by PT or CT inhibits the GTP-induced increase in ankyrin binding to GP85 (CD44). In addition to GP85 (CD44) being the first reported transmembrane GTP-binding protein, these results suggest that GTP plays an important role in promoting the interaction between GP85 (CD44) and its underlying membrane cytoskeleton through ankyrin.
AB - In this study, we have used photoaffinity labeling by [32P]azido-GTP as well as [32P]ADP-ribosylation by pertussis toxin (PT) and cholera toxin (CT) to identify GTP-binding proteins associated with mouse T-lymphoma plasma membranes. Our results indicate that GP85 (CD44) can be photoaffinity labeled by [32P] azido-GTP and [32P]ADP-ribosylated by both PT and CT. Using purified GP85 (CD44) obtained by Triton X-100 extraction, wheat germ agglutinin-Sepharose, and anti-GP85 (CD44) antibody affinity chromatographies, we have further characterized GP85 (CD44) as a GTP-binding protein. GP85 (CD44) is found to bind guanosine 5′-3-O-(thio)triphosphate (GTPγS) in a time- and dose-dependent manner with a dissociation constant of 0.83 nM. Importantly, GP85 (CD44) appears to display a GTPase activity which hydrolyzes [γ-32P]GTP at a rate of 0.011 mol of Pi released/mol of GP85 (CD44)/min. This GTPase activity can be readily inhibited by PT- or CT-mediated ribosylation of GP85 (CD44). Most interestingly, GTP binding significantly enhances the interaction of purified GP85 (CD44) with ankyrin, whereas ADP-ribosylation of GP85 (CD44) by PT or CT inhibits the GTP-induced increase in ankyrin binding to GP85 (CD44). In addition to GP85 (CD44) being the first reported transmembrane GTP-binding protein, these results suggest that GTP plays an important role in promoting the interaction between GP85 (CD44) and its underlying membrane cytoskeleton through ankyrin.
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M3 - Article
C2 - 1429559
AN - SCOPUS:0026574819
SN - 0021-9258
VL - 267
SP - 22073
EP - 22078
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 31
ER -