Ku is a complex of 7OkDa and 86kDa proteins, found in the nucleus of human cells where it binds DNA and is the target of autoantibodies in several autoimmune conditions. We have now demonstrated that both the 7OkDa and 86kDa components of Ku are present in small amounts on the cell surface and that they are integral membrane proteins. By use of antibodies to synthetic peptides, derived from the 7OkDa protein sequence and fluorescein-activated cell sorting we demonstrated that several different domains are exposed on the cell surface. Synthetic peptides were used to identify the domains of the 7OkDa protein which bind DNA. By slot blot analysis one peptide of 15 amino acids (peptide 25A) bound DNA with very high affinity and was able to inhibit the binding of the recombinant 7OkDa protein to DNA. Another peptide (peptide 4) although contains a number of basic amino acids and is contiguous with one of the leucine zipper regions in the protein bound DNA weakly. The use of short peptides to identify DNA binding domains is original and may have broad applicability to other DNA binding proteins. Efforts are underway to understand the normal cellular function of this protein. Studies are continuing on cloning of autoantigens involved in diabetes mellitus. Two cDNA clones, (which are preferentially expressed in human insulinoma), were isolated from an insulinoma glucagonoma subtraction library. One clone, IG-3, detected a transcript of 2.4 kb in human insulinoma tissue. Another cDNA clone IG-20 detected a 5.0 kb transcript in human insulinoma, and at a lower level in the brain. Partial DNA sequence analysis of this clone revealed no homology to known gene sequences and thus represents a unique gene. Studies are underway to characterize these genes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Intramural Research (Z01)
Project #
1Z01DE000423-05
Application #
3875223
Study Section
Project Start
Project End
Budget Start
Budget End
Support Year
5
Fiscal Year
1990
Total Cost
Indirect Cost
Name
National Institute of Dental & Craniofacial Research
Department
Type
DUNS #
City
State
Country
United States
Zip Code
Cai, Tao; Hirai, Hiroki; Fukushige, Tetsunari et al. (2009) Loss of the transcriptional repressor PAG-3/Gfi-1 results in enhanced neurosecretion that is dependent on the dense-core vesicle membrane protein IDA-1/IA-2. PLoS Genet 5:e1000447
Kim, Soo Mi; Theilig, Franziska; Qin, Yan et al. (2009) Dense-core vesicle proteins IA-2 and IA-2{beta} affect renin synthesis and secretion through the {beta}-adrenergic pathway. Am J Physiol Renal Physiol 296:F382-9
Khil, L-Y; Jun, H-S; Kwon, H et al. (2007) Human chorionic gonadotropin is an immune modulator and can prevent autoimmune diabetes in NOD mice. Diabetologia 50:2147-55
Notkins, Abner Louis (2007) New predictors of disease. Molecules called predictive autoantibodies appear in the blood years before people show symptoms of various disorders. Tests that detected these molecules could warn of the need to take preventive action. Sci Am 296:72-9
Mett, Vadim; Shamloul, Abdel-Moneim; Hirai, Hiroki et al. (2007) Engineering and expression of the intracellular domain of insulinoma-associated tyrosine phosphatase (IA-2ic), a type 1 diabetes autoantigen, in plants. Transgenic Res 16:77-84
Harashima, S-I; Harashima, C; Nishimura, T et al. (2007) Overexpression of the autoantigen IA-2 puts beta cells into a pre-apoptotic state: autoantigen-induced, but non-autoimmune-mediated, tissue destruction. Clin Exp Immunol 150:49-60
Li, Na; Shigihara, Toshikatsu; Tzioufas, Athanasios G et al. (2007) Human chorionic gonadotropin prevents Sjogren's syndrome-like exocrinopathy in mice. Arthritis Rheum 56:2211-5
Kubosaki, Atsutaka; Nakamura, Shinichiro; Clark, Anne et al. (2006) Disruption of the transmembrane dense core vesicle proteins IA-2 and IA-2beta causes female infertility. Endocrinology 147:811-5
Kubosaki, Atsutaka; Nakamura, Shinichiro; Notkins, Abner Louis (2005) Dense core vesicle proteins IA-2 and IA-2beta: metabolic alterations in double knockout mice. Diabetes 54 Suppl 2:S46-51
Hu, Y F; Zhang, H L; Cai, T et al. (2005) The IA-2 interactome. Diabetologia 48:2576-81

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