The
post-translational arginylation of proteins is the covalent union of arginine
to an acidic amino acid at the N-terminal position mediated by arginyl-tRNA
protein transferase (Ate 1). We demonstrated the posttranslational arginylation
of calreticulin (CRT) in vitro and in living cells. The arginylated form of CRT
(R-CRT) is present in the citosol, in contrast to the non arginylated CRT,
resident of endoplasmatic reticulum.
It
has been shown that CRT affects cell adhesion by regulating vinculin expression.
This may be mediated by direct interaction between CRT and the KxGFFKR of a integrins, that imply a cytoplasmic localization of
CRT.
By
immunocytochemistry, using an antibody against R-CRT we observed an enhanced
colocalization of R-CRT and vinculin in cells subjected to focal adhesion disassembly
and reassembly, similarly to that observed between RCRT and integrins. Further studies
performed in cells lacking Ate1 (ate1 -/-) show a differential attachment to
laminin and polylisine when compared to cells ate1 +/+. After transfection with
CRT the ate1 -/- cells did not improve their adhesiveness to substrata as ate1
+/+ cells.
Thus,
this evidence supports the idea that R-CRT is implicated in cell adhesion and
posttranslational arginylation of CRT seems to regulate its cytosolic function.
Supported by
SECyT-UNC, CONICET, ANPCyT-PICT.
