Disruption of ligand binding to the insulin-like growth factor II/mannose 6-phosphate receptor by cancer-associated missense mutations.
The insulin-like growth factor II/mannose 6-phosphate receptor (IGF2R) carries out multiple regulatory and transport functions, and disruption of IGF2R function has been implicated as a mechanism to increase cell proliferation. Several missense IGF2R mutations have been identified in human cancers, including the following amino acid substitutions occurring in the extracytoplasmic domain of the receptor: Cys-1262 --> Ser, Gln-1445 --> His, Gly-1449 --> Val, Gly-1464 --> Glu, and Ile-1572 --> Thr. To determine what effects these mutations have on IGF2R function, mutant and wild-type FLAG epitope-tagged IGF2R constructs lacking the transmembrane and cytoplasmic domains were characterized for binding of insulin-like growth factor (IGF)-II and a mannose 6-phosphate-bearing pseudoglycoprotein termed PMP-BSA (where PMP is pentamannose phosphate and BSA is bovine serum albumin). The Ile-1572 --> Thr mutation eliminated IGF-II binding while not affecting PMP-BSA binding. Gly-1449 --> Val and Cys-1262 --> Ser each showed 30-60% decreases in the number of sites available to bind both (125)I-IGF-II and (125)I-PMP-BSA. In addition, the Gln-1445 --> His mutant underwent a time-dependent loss of IGF-II binding, but not PMP-BSA binding, that was not observed for wild type. In all, four of the five cancer-associated mutants analyzed demonstrated altered ligand binding, providing further evidence that loss of IGF2R function is characteristic of certain cancers.
Byrd
J C
JC
Department of Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Nebraska 68198-4525, USA.
Devi
G R
GR
de Souza
A T
AT
Jirtle
R L
RL
MacDonald
R G
RG
D001665:Binding Sites; D001667:Binding, Competitive; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D019656:Loss of Heterozygosity; D008360:Mannosephosphates / Q000378:metabolism*; D020125:Mutation, Missense; D009369:Neoplasms / Q000235:genetics*; D017527:Receptor, IGF Type 2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
D008360:Mannosephosphates; D017527:Receptor, IGF Type 2; C027693:mannose-6-phosphate; D007335:Insulin-Like Growth Factor II