LMBD1 protein serves as a specific adaptor for insulin receptor internalization.
Energy homeostasis is crucial for maintaining normally functioning cells; disturbances in this balance often cause various diseases. The limb region 1 (LMBR1) domain containing 1 gene (lmbrd1) encodes the LMBD1 protein that possesses 9 putative transmembrane domains. LMBD1 has been suggested to be involved in the lysosome in aiding the export of cobalamin. In this study, we determined that LMBD1 plays a regulatory role in the plasma membrane. A micro-positron emission tomography analysis showed that a single-allele knock-out of lmbrd1 increased the (18)F-fluorodeoxyglucose uptake in murine hearts. In addition, the knockdown of lmbrd1 resulted in an up-regulated signaling of the insulin receptor (IR) and its downstream signaling molecule, Akt. Confocal and live total internal reflection fluorescence microscopy showed that LMBD1 co-localized and co-internalized with clathrin and the IR, but not with the transferrin receptor. The results of the mutation analysis and phenotypic rescue experiments indicate that LMBD1 interacts with adaptor protein-2 and is involved in the unique clathrin-mediated endocytosis of the IR. LMBD1 selectively interacts with the IR. The knockdown of lmbrd1 attenuated IR endocytosis, resulting in the perturbation of the IR recycling pathway and consequential enhancement of the IR signaling cascade. In summary, LMBD1 plays an imperative role in mediating and regulating the endocytosis of the IR.
From the Institute of Biochemistry and Molecular Biology.
Linda Tzu-Ling
LT
Tseng
From the Institute of Biochemistry and Molecular Biology.
Chieh-Liang
CL
Lin
the Department of Nuclear Medicine, National Taiwan University Hospital, Taipei 10041, Taiwan.
Kai-Yuan
KY
Tzen
the Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.
Shin C
SC
Chang
From the Institute of Biochemistry and Molecular Biology. Electronic address: mfchang@ntu.edu.tw.
Ming-Fu
MF
Chang
D033962:Adaptor Protein Complex 2 / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002966:Clathrin / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology; D055785:Gene Knockdown Techniques; D006801:Humans; D051379:Mice; D008817:Mice, Mutant Strains; D009206:Myocardium / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000235:genetics / Q000378:metabolism*; D049268:Positron-Emission Tomography; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D019275:Radiopharmaceuticals / Q000494:pharmacology; D051381:Rats; D011972:Receptor, Insulin / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D033962:Adaptor Protein Complex 2; D002966:Clathrin; C502888:LMBRD1 protein, human; D029543:Nucleocytoplasmic Transport Proteins; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D011972:Receptor, Insulin; D051057:Proto-Oncogene Proteins c-akt
Akt; Antisense RNA; Cell Signaling; Cell Surface Receptor; Confocal Microscopy; Endocytosis; Flow Cytometry; Glucose Metabolism; In Vivo Imaging; Insulin