Disease relevance of INSM1

• Further studies showed that both INSM1 and CAP proteins were present in the nucleus of insulinoma cells and that endogenous INSM1 protein was co-precipitated with antibody to CAP [1].
• The INSM1 promoter is therefore a potential novel tool for transcriptionally targeted gene therapy for neuroendocrine tumors [2].
• We analyzed expression of a reporter gene from a 1.7 kb region of the INSM1 promoter in a large number of small-cell lung cancer (SCLC) cell lines [2].
• Expression of the suicide gene herpes simplex virus thymidine kinase (HSV-TK) from the INSM1 promoter in combination with treatment with the prodrug ganciclovir (GCV) caused a significant increase in GCV sensitivity specifically in INSM1-expressing cell lines [2].
• In this paper, the regulatory elements and the promoter region of the 5'-upstream region were analyzed by use of a series of deletion mutants (ranging from +26 bp to -2090 bp upstream of the IA-1 gene), which were tested in a pituitary tumor cell line, AtT-20, and Hela cells by transient transfection assays [3].

High impact information on INSM1

• The Zinc-finger factor Insm1 (IA-1) is essential for the development of pancreatic beta cells and intestinal endocrine cells [4].
• MAIN OUTCOME MEASURES: BCA was defined as elevated levels of insulin autoantibody, glutamic acid decarboxylase autoantibody, or insulinoma-associated islet tyrosine phosphatases autoantibody (IA-2) above the 99th percentile of 198 normal subjects [5].
• In this report we describe the expression of IA-1 mRNA in a panel of 64 human lung cell lines [6].
• IA-1 is a recently isolated novel complementary DNA which encodes a protein of 510 amino acids that contains both a zinc finger DNA-binding domain and a putative prohormone domain. mRNA expression of IA-1 has been found thus far only in tumors of neuroendocrine origin [6].
• In most of the lung cancer cell lines examined, IA-1 showed high concordance with the other neuroendocrine markers, L-dopa decarboxylase, and chromogranin A. The one exception was a variant small cell lung cancer cell line which expressed low or nondetectable levels of L-dopa decarboxylase [6].
• INSM1 can promote pancreatic duct-to-beta cell conversion, through transcription regulation of certain ITFs like Pax6, Nkx6.1, etc [7] .

Chemical compound and disease context of INSM1

• Insulinoma associated with a case of multiple endocrine neoplasia type I: Functional somatostatin receptors and abnormal glucose-induced insulin secretion [8].

Biological context of INSM1

• A chromatin immunoprecipitation assay confirmed that in vivo INSM1 is situated on the promoter region of the neuroD/beta2 gene [9].
• We have identified an INSM1 binding site in the neuroD/beta2 promoter and demonstrated transcriptional repressor activity of INSM1 by transient transfection assay [9].
• In an attempt to elucidate the molecular mechanism of transcriptional repression by the INSM1 gene, cyclin D1 was identified as an interacting protein by using a 45-day-old human foetal brain cDNA library and a yeast two-hybrid screen [9].
• Mouse INSM1 was found to be 86% identical to human INSM1 and both proteins contain proline-rich regions and multiple zinc-finger DNA-binding motifs [1].
• These findings raise the possibility that during embryo development CAP may enter the nucleus through its own nuclear localization signal or by binding to INSM1 [1].

Anatomical context of INSM1

• METHODOLOGY: To examine whether the IA-1 gene is associated with pancreatic endocrine cell differentiation, we used a rat pancreatic amphicrine cell line, AR42J, to investigate whether the expression of the IA-1 gene coincides with AR42J cells converting into either endocrine or exocrine lineage [10].
• These findings suggest that the IA-1 protein may be auto-regulated and play a role in pancreas and neuronal development, specifically in the regulation of the NeuroD/beta2 gene [11].
• IA-2-dependent IFN-gamma secretion was induced in CD4(+) cells from spleen as well as pancreatic and mesenteric lymph [12].
• We now report that T cell responses to IA-2 can also be detected in the nonobese diabetic (NOD) mouse, a model of human IDDM [12].
• In 50 patients with recent-onset type 1 diabetes, antibodies to GAD and insulinoma-associated antigen 2 (IA-2) were analyzed by radioimmunoassay; cytoplasmic islet cell antibodies were determined by indirect immunofluorescence [13].

Associations of INSM1 with chemical compounds

• 1. In contrast, dramatically decreased expression of mRNA for IA-1 and islet-specific transcription factors was displayed when AR42J cells were converted into the acinar-like phenotype by dexamethasone [10].
• Insulinoma-associated protein (IA)-2beta, also known as phogrin, is an enzymatically inactive member of the transmembrane protein tyrosine phosphatase family and is located in dense-core secretory vesicles [14].
• The regioisomers with the N-phenyl on pyrrole rings A and D are obtained in a 2:1 ratio with isozyme IA1, 1:1 with IIB2, 1:1.7 with IIB1, and 1:2 with IIE1 [15].
• However, the Pvd- Pch+ strain (211-5) had no observable advantage over the Pvd- Pch- strain, IA1, during incubation in human serum [16].

Other interactions of INSM1

• A further chromatin immunoprecipitation assay confirmed that HDAC-3 occupies this same region of the neuroD/beta2 promoter, by forming a transcription complex with INSM1 [9].
• Neuroendocrine differentiation factor, IA-1, is a transcriptional repressor and contains a specific DNA-binding domain: identification of consensus IA-1 binding sequence [11].
• High expression was observed for a number of cell lines, but unlike for the INSM1 promoter, reporter gene expression from the GRP promoter did not correlate to the relative GRP mRNA levels, demonstrating that this region may not contain all necessary regulatory elements [2].
• Furthermore, this insulinoma associated expression of PAX4 mRNA was accompanied with expression of its novel variant form (PAX4v) [17].
• Neither the frequency of severe hypoglycemia nor positivity to GAD65 and insulinoma-associated protein 2 antibodies was associated with increased weight gain with either intensive or conventional therapy [18].

Analytical, diagnostic and therapeutic context of INSM1

• We identified proteins that interacted with INSM1 by the yeast two-hybrid system and the binding of one of them, Cbl-associated protein (CAP), to INSM1 was confirmed by in vitro pull-down experiments, nuclear colocalization, and co-immunoprecipitation assays [1].
• Northern blot analysis revealed IA-1 mRNA in five of five human insulinoma and three of three murine insulinoma cell lines [19].
• In situ hybridization localized the IA-1 gene to the short arm of human chromosome 20 [20].
• Sequence analysis and restriction enzyme mapping showed that the IA-1 gene is uninterrupted and appears to be intronless [20].
• During a mean observation period of 4.7 years, autoantibodies to insulin, anti-glutamic acid decarboxylase and insulinoma-associated antigen-2 were measured by radiobinding assays, and islet cell antibodies (ICA) by immunofluorescence [21].

References