Dominant-negative effect of truncated mannose 6-phosphate/insulin-like growth factor II receptor species in cancer.
Oligomerization of the mannose 6-phosphate/insulin-like growth factor II receptor (M6P/IGF2R) is important for optimal ligand binding and internalization. M6P/IGF2R is a tumor suppressor gene that exhibits loss of heterozygosity and is mutated in several cancers. We tested the potential dominant-negative effects of two cancer-associated mutations that truncate M6P/IGF2R in ectodomain repeats 9 and 14. Our hypothesis was that co-expression of the truncated receptors with the wild-type/endogenous full-length M6P/IGF2R would interfere with M6P/IGF2R function by heterodimer interference. Immunoprecipitation confirmed formation of heterodimeric complexes between full-length M6P/IGF2Rs and the truncated receptors, termed Rep9F and Rep14F. Remarkably, increasing expression of either Rep9F or Rep14F provoked decreased levels of full-length M6P/IGF2Rs in both cell lysates and plasma membranes, indicating a dominant-negative effect on receptor availability. Loss of full-length M6P/IGF2R was not due to increased proteasomal or lysosomal degradation, but instead arose from increased proteolytic cleavage of cell-surface M6P/IGF2Rs, resulting in ectodomain release, by a mechanism that was inhibited by metal ion chelators. These data suggest that M6P/IGF2R truncation mutants may contribute to the cancer phenotype by decreasing the availability of full-length M6P/IGF2Rs to perform tumor-suppressive functions such as binding/internalization of receptor ligands such as insulin-like growth factor II.
Department of Chemistry, University of Nebraska at Omaha, Omaha, NE 68198, USA.
Jodi L
JL
Kreiling
Michelle A
MA
Montgomery
Joseph R
JR
Wheeler
Jennifer L
JL
Kopanic
Christopher M
CM
Connelly
Megan E
ME
Zavorka
Jenna L
JL
Allison
Richard G
RG
Macdonald
D000595:Amino Acid Sequence; D001483:Base Sequence; D002462:Cell Membrane / Q000378:metabolism; D018076:DNA, Complementary / Q000235:genetics; D019281:Dimerization; D005110:Extracellular Space / Q000378:metabolism; D057809:HEK293 Cells; D006207:Half-Life; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D016296:Mutagenesis; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017527:Receptor, IGF Type 2 / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
D018076:DNA, Complementary; D050505:Mutant Proteins; D010446:Peptide Fragments; D017527:Receptor, IGF Type 2; D011994:Recombinant Proteins; D025521:Tumor Suppressor Proteins; D046988:Proteasome Endopeptidase Complex