The transmembrane protein CBP plays a role in transiently anchoring small clusters of Thy-1, a GPI-anchored protein, to the cytoskeleton.
It remains unclear how GPI-anchored proteins (GPIAPs), which lack cytoplasmic domains, transduce signals triggered by specific ligation. Such signal transduction has been speculated to require the ligated GPIAP to associate with membrane-spanning proteins that communicate with obligate cytoplasmic proteins. Transient anchorage of crosslinked proteins on the cell surface was previously characterized by single-particle tracking, and temporary association with the actin cytoskeleton was hypothesized to cause regulated anchorage. GPIAPs, such as Thy-1, require clustering, cholesterol and Src-family kinase (SFK) activity to become transiently anchored. By contrast, a transmembrane protein, the cystic fibrosis transmembrane conductance regulator (CFTR), which has a PDZ-binding motif in its cytoplasmic C-terminus that binds the ERM adaptor EBP50, exhibits anchorage that strictly requires EBP50 but has little dependence on cholesterol or SFK. We hypothesized that a transmembrane protein would be required to mediate the linkage between Thy-1 and the cytoskeleton. Here, we present evidence, obtained by shRNA knockdown, that the transmembrane protein Csk-binding protein (CBP) plays an obligatory role in the transient anchorage of Thy1. Furthermore, either a dominant-negative form of CBP that did not bind EBP50 or a dominant-negative EBP50 drastically reduced transient anchorage of Thy-1, indicating the involvement of this adaptor. Finally, we speculate on the role of phosphorylation in the regulation of transient anchorage.
Chen
Yun
Y
Department of Cell and Developmental Biology, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7090, USA.
Veracini
Laurence
L
Benistant
Christine
C
Jacobson
Ken
K
D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism*; D017261:Glycosylphosphatidylinositols / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D018800:Thy-1 Antigens / Q000235:genetics / Q000378:metabolism*
D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; C498709:Pag1 protein, mouse; D010750:Phosphoproteins; D018800:Thy-1 Antigens