Cf. Jie et al., Posttranslational processing and differential glycosylation of Tractin, anIg-superfamily member involved in regulation of axonal outgrowth, BBA-PROT ST, 1479(1-2), 2000, pp. 1-14
Citations number
58
Categorie Soggetti
Biochemistry & Biophysics
Journal title
BIOCHIMICA ET BIOPHYSICA ACTA-PROTEIN STRUCTURE AND MOLECULAR ENZYMOLOGY
Tractin is a novel member of the Ig-superfamily which has a highly unusual
structure. It contains six Ig domains, four FNIII-like domains, an acidic d
omain, 12 repeats of a novel proline- and glycine-rich motif with sequence
similarity to collagen, a transmembrane domain, and an intracellular tail w
ith an ankyrin and a PDZ domain binding motif. By generating domain-specifi
c antibodies, we show that Tractin is proteolytically processed at two clea
vage sites, one located in the third FNIII domain, and a second located jus
t proximal to the transmembrane domain resulting in the formation of four f
ragments. The most NH2-terminal fragment which is glycosylated with the Lan
3-2, Lan4-2, and Laz2-369 glycoepitopes is secreted, and we present evidenc
e which supports a model in which the remaining fragments combine to form a
secreted homodimer as well as a transmembrane heterodimer. The extracellul
ar domain of the dimers is mostly made up of the collagen-like PG/YG-repeat
domain but also contains 11/2 FNIII domain and the acidic domain. The coll
agen-like PG/YG-repeat domain could be selectively digested by collagenase
and we show by yeast two-hybrid analysis that the intracellular domain of T
ractin can interact with ankyrin. Thus, the transmembrane heterodimer of Tr
actin constitutes a novel protein domain configuration where sequence that
has properties similar to that of extracellular matrix molecules is directl
y linked to the cytoskeleton through interactions with ankyrin. (C) 2000 El
sevier Science B.V. All rights reserved.