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Functional analysis of LKB1/STK11 mutants and two aberrant isoforms found in Peutz‐Jeghers Syndrome patients
Author(s) -
Boudeau J.,
Kieloch A.,
Alessi D.R.,
Stella A.,
Guanti G.,
Resta N.
Publication year - 2003
Publication title -
human mutation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.981
H-Index - 162
eISSN - 1098-1004
pISSN - 1059-7794
DOI - 10.1002/humu.9112
Subject(s) - stk11 , biology , mutant , threonine , serine , autophosphorylation , kinase , wild type , phosphorylation , cancer research , protein kinase a , chromosomal translocation , microbiology and biotechnology , mutation , genetics , gene , kras
Abstract Peutz‐Jeghers Syndrome (PJS) is thought to be caused by mutations occurring in the widely expressed serine/threonine protein kinase named LKB1/STK11. Recent work has led to the identification of four mutants (R304W, I177N, K175‐D176del, L263fsX286) and two novel aberrant LKB1/STK11 cDNA isoforms (r291‐464del, r485‐1283del) in a group of PJS Italian patients. Three of the four mutations only change 1 or 2 amino acids in the LKB1/STK11 catalytic domain. Here we demonstrate that all six LKB1/STK11variants analysed are completely inactive in vitro as they were unable to autophosphorylate at Thr336, the major LKB1/STK11 autophosphorylation site, and to phosphorylate the p53 tumour suppressor protein. We also show that 5 out of the 6 variants are entirely localised in the nucleus in contrast to the wild type LKB1/STK11, which is detected in both the nucleus and cytoplasm. Finally we demonstrate that all 6 LKB1/STK11 variants, in contrast to wild type LKB1/STK11, are unable to suppress the growth of melanoma G361 cells. Taken together, these results demonstrate that the LKB1 mutations investigated in this study lead to the loss of serine/threonine kinase activity and are therefore likely to be the primary cause of PJS development in the patients that they were isolated from. © 2003 Wiley‐Liss, Inc.