These Lnpep (or IRAP) knockout mice exhibit an impaired insulin response and decreased levels of GLUT4, but maintain normal glucose homeostasis.
Susanna Keller, University of Virginia
Lnpep (leucyl/cystinyl aminopeptidase, also called IRAP) is a zinc-dependent aminopeptidase that cleaves peptide hormones. In response to insulin administration, LNPEP and the insulin-responsive glucose transporter SLC2A4 (or GLUT4) translocate from the intracellular compartments of fat and muscle cells to the plasma membrane. Mice homozygous for this null allele exhibit an impaired response to insulin, reduced glucose uptake in isolated adipocytes and the extensor digitorum longus muscle, but not the soleus muscle. Despite a 40-85% decrease in GLUT4 levels, mice maintain normal glucose homeostasis. LNPEP regulates vasopressin cleavage and mice homozygous for this null allele show increased circulating vasopressin levels and impaired vasopressin cleavage in response to insulin. Vasopressin is a physiological substrate for the insulin-regulated aminopeptidase IRAP.
A targeting vector containing the neomycin resistance cassette was used to replace exons 2 through 6 and the intervening introns through homologous recombination. Exons 2-6 encode the cytoplasmic tail required for subcellular localization and insulin regulation, the transmembrane domain and a zinc-binding site required for catalytic activity. The construct was electroporated into 129S/SvEv-derived embryonic stem (ES) cells. Correctly targeted ES cells were injected into blastocysts. The resulting chimeric animals were crossed to 129S/SvEv mice and then backcrossed to C57BL/6 using a speed congenic approach. Upon arrival at The Jackson Laboratory, mice were bred to C57BL/6J for at least 1 generation to establish the colony.
|Allele Name||targeted mutation 1, Susanna R Keller|
|Allele Type||Targeted (Null/Knockout)|
|Gene Symbol and Name||Lnpep, leucyl/cystinyl aminopeptidase|
|Strain of Origin||129S/SvEv|
|Molecular Note||Exons 2 through 6 and their intervening introns were replaced with a neomycin resistance gene. The deleted region included sequence encoding the cytoplasmic tail involved in subcellular localization and regulation, the transmembrane domain, and the zinc binding site that is essential for catalytic activity. Western blot analysis indicated an absence of normal protein in homozygous mutant mice.|
While maintaining a live colony, these mice are bred as homozygotes.
When using the IRAP- mouse strain in a publication, please cite the originating article(s) and include JAX stock #027187 in your Materials and Methods section.
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