LCHN is a protein that in humans is encoded by the KIAA1147 gene (NCBI Gene ID 57189) located on chromosome 7. [1] It is likely part of the tripartite DENN domain family of proteins that often function as Rab-GEFs [2] [3] to regulate vesicular trafficking. [2] Both the mRNA and protein have been shown to be upregulated following ischemic stroke, [4] and to be produced at altered levels in patients with FTD-ALS, [5] however the gene's contribution to these states is not well understood.
KIAA1147 is located on the 7th chromosome in humans from bases 141652381-141702188 on the negative strand. [6] Additional names for KIAA1147 include PRO25611, [7] AI841796 in the mouse [8] and RGD1563986 in the rat. [9] Only one mRNA transcript of KIAA1147 has been reported in NCBI, and is composed of 9 exons. [1]
Human LCHN is a cytoplasmic protein composed of 455 amino acids predicted to be 51.4 kD before modifications with isoelectric point of 5.06. [10] The majority of its 455 amino acids make up the tripartite DENN domains which are commonly found in proteins that act as Rab-GEFs [2] and regulate vesicular trafficking. [2] LCHN has several predicted phosphorylation sites [11] and contains many motifs for kinase binding. [12] The uDENN and cDENN domains of LCHN are predicted to be primarily coil, while the dDENN domain is predicted to be a combination of alpha helix and beta sheet. [13] [14] [15] The cDENN domain is the most highly conserved domain within DENN family proteins, [2] and is also primarily coil in protein DENND1B, [16] which has been crystallized and confirmed to interact with the guanine nucleotide exchange domain of Rab-35. [16] LCHN also contains a Stability of Polarity Axis (SPA) region. [6] that may allow it to play a role in cell division. [17]
The Human Protein Atlas reports high levels of KIAA1147 transcription in several brain regions including cerebral cortex, cerebellum, and retina, as well as non-brain regions including spleen, thymus, stomach, prostate, lung, and ascending colon. [18] Immunohistochemistry has shown LCHN to be localized to the cytoplasmic face of the Golgi apparatus in cell culture, [19] and the brain in mouse fetal development. [20] In the adult mouse and human brain, LCHN is expressed relatively ubiquitously. [21] [22] Expression of LCHN has been shown to increase in response to chronic alcoholism, [23] immature and mature dendritic response to hypoxia, and ischemic stroke. [4]
There are binding sites for two main groups of transcription factors in the predicted promoter of KIAA1147. The first group consists of elements related to the cell cycle and neuronal development and includes AP-2, NRF1, BRAC, E2F, NEUR, and NRSF. [24] The second consists of elements related to brain insult, including HIFF (hypoxia inducible factor), CREB (cAMP responsive factor linked to ER stress response), GREF (glucocorticoid responsible factor), HEAT (heat shock responsive factor), and HDBP (Huntington's disease regulatory binding protein). [24] In patients with FTD-ALS, there has been reported abnormal upstream CpG methylation of KIAA1147 [5]
Yeast two-hybrid assays have shown LCHN to physically interact with SETBP1, [25] a protein that contains 3 nuclear localization signals. [26] Despite the lack of a predicted nuclear localization signal in its own sequence, this interaction suggests that LCHN may be able to enter and have functional importance in the nucleus.
In affinity chromatography studies, LCHN has been reported to have a physical association with TGOLN2, [27] [28] a surface protein of the Golgi apparatus. [29] This likely explains immunohistochemical finding of strong LCHN localization near the Golgi apparatus [19] despite being a predicted cytoplasmic protein. [10]
Affinity chromatography studies have also reported a physical association between LCHN and kallikreins KLK5 and KLK11, [27] [28] serine proteases. [30] It is possible that cleavage by these proteases may be relevant to LCHN's function.
LCHN has been reported to be capable of a physical association with EFNB3, [27] an ephrin receptor ligand with reported importance in neuronal development. [31] This, coupled with the high expression of LCHN in the developing central nervous system, suggests that binding of LCHN to EFNB3 may modulate neuronal development.
LCHN expression has been reported to be unregulated following ischemic stroke, chronic alcoholism, and cell culture responses of immature and mature dendrites to prolonged hypoxia. [4] [23] Additionally, decreased expression as a result of CpG methylation has been implicated to be pathogenic in patients with FTD-ALS. [5] Within the predicted promoter of KIAA1147, there are predicted binding sites for hypoxia response elements that would accompany ischemic stroke, heat shock proteins, factors related to the glucocorticoid mediated stress response, and cAMP responsive factors related to the ER stress response. [32] Due to the reported evidence of LCHN upregulation following ischemic stroke, which often results in neuronal damage or death, [33] as well presence of several binding sites for factors induced by rapid trauma to the brain, [24] it is likely that KIAA1147 plays a role in the brain’s response to sudden stress and injury.
The presence of the SPA domain within LCHN suggests that it may play a role in cell division. [6] [17] LCHN has been shown to physically associate with EFNB3, a protein with reported importance in neuronal development. [27] [31] A second reported association with SETBP1 may open up the possibility for LCHN to play a role in cell cycle regulation from within the nucleus. [25] [26] The predicted KIAA1147 promoter contains binding sites for cell-division related factors and factors known to have specific expression during neuronal development. RNA in situ hybridization has shown KIAA1147 to be located at high levels in the developing brain. Together, these data suggest that LCHN plays a role in regulating cellular division during development of the brain.
LCHN has been shown to be upregulated following a number of insults to the brain including the response to chronic alcoholism, immature and mature dendritic response to hypoxia, and ischemic stroke. [4] [23] Recent studies have implicated abnormal CpG methylation of LCHN in FTD-ALS. [5] No disease causing SNPs in LCHN have been reported with high frequency. [34]
There are no reported paralogs of LCHN in humans. [1] LCHN homologs exist in animals dating back to the earliest sponges, with a notable lack of reported expression in Drosophila and C. elegans . [1] There are also a number of LCHN homologs in protists including choanoflagellates, amoeba, and algae, as well as other unicellular eukaryotes including fungi. [1]
Protein YIF1A is a Yip1 domain family proteins that in humans is encoded by the YIF1A gene.
C8orf48 is a protein that in humans is encoded by the C8orf48 gene. C8orf48 is a nuclear protein specifically predicted to be located in the nuclear lamina. C8orf48 has been found to interact with proteins that are involved in the regulation of various cellular responses like gene expression, protein secretion, cell proliferation, and inflammatory responses. This protein has been linked to breast cancer and papillary thyroid carcinoma.
The coiled-coil domain containing 142 (CCDC142) is a gene which in humans encodes the CCDC142 protein. The CCDC142 gene is located on chromosome 2, spans 4339 base pairs and contains 9 exons. The gene codes for the coiled-coil domain containing protein 142 (CCDC142), whose function is not yet well understood. There are two known isoforms of CCDC142. CCDC142 proteins produced from these transcripts range in size from 743 to 665 amino acids and contain signals suggesting protein movement between the cytosol and nucleus. Homologous CCDC142 genes are found in many animals including vertebrates and invertebrates but not fungus, plants, protists, archea, or bacteria. Although the function of this protein is not well understood, it contains a coiled-coil domain and a RINT1_TIP1 motif located within the coiled-coil domain.
PRR29 is a protein encoded by the PRR29 gene located in humans on chromosome 17 at 17q23.
Uncharacterized protein Chromosome 16 Open Reading Frame 71 is a protein in humans, encoded by the C16orf71 gene. The gene is expressed in epithelial tissue of the respiratory system, adipose tissue, and the testes. Predicted associated biological processes of the gene include regulation of the cell cycle, cell proliferation, apoptosis, and cell differentiation in those tissue types. 1357 bp of the gene are antisense to spliced genes ZNF500 and ANKS3, indicating the possibility of regulated alternate expression.
BEND2 is a protein that in humans is encoded by the BEND2 gene. It is also found in other vertebrates, including mammals, birds, and reptiles. The expression of BEND2 in Homo sapiens is regulated and occurs at high levels in the skeletal muscle tissue of the male testis and in the bone marrow. The presence of the BEN domains in the BEND2 protein indicates that this protein may be involved in chromatin modification and regulation.
Chromosome 21 Open Reading Frame 58 (C21orf58) is a protein that in humans is encoded by the C21orf58 gene.
C16orf82 is a protein that, in humans, is encoded by the C16orf82 gene. C16orf82 encodes a 2285 nucleotide mRNA transcript which is translated into a 154 amino acid protein using a non-AUG (CUG) start codon. The gene has been shown to be largely expressed in the testis, tibial nerve, and the pituitary gland, although expression has been seen throughout a majority of tissue types. The function of C16orf82 is not fully understood by the scientific community.
Forkhead-associated domain containing protein 1 (FHAD1) is a protein encoded by the FHAD1 gene.
C15orf39 is a protein that in humans is encoded by the Chromosome 15 open reading frame 15 (C15orf39) gene.
Chromosome 9 open reading frame 43 is a protein that in humans is encoded by the C9orf43 gene. The gene is also known as MGC17358 and LOC257169. C9orf43 contains DUF 4647 and a polyglutamine repeat region although protein function is not well understood.
Uncharacterized protein C16orf86 is a protein in humans that is encoded by the C16orf86 gene. It is mostly made of alpha helices and it is expressed in the testes, but also in other tissues such as the kidney, colon, brain, fat, spleen, and liver. For the function of C16orf86, it is not well understood, however it could be a transcription factor in the nucleus that regulates G0/G1 in the cell cycle for tissues such as the kidney, brain, and skeletal muscles as mentioned in the DNA microarray data below in the gene level regulation section.
Cilia- and flagella-associated protein 299 (CFAP299), is a protein that in humans is encoded by the CFAP299 gene. CFAP299 is predicted to play a role in spermatogenesis and cell apoptosis.
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Chromosome 1 open reading frame 141, or C1orf141 is a protein which, in humans, is encoded by gene C1orf141. It is a precursor protein that becomes active after cleavage. The function is not yet well understood, but it is suggested to be active during development
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TEKTIP1, also known as tektin-bundle interacting protein 1, is a protein that in humans is encoded by the TEKTIP1 gene.
THAP domain-containing protein 3 (THAP3) is a protein that, in Homo sapiens (humans), is encoded by the THAP3 gene. The THAP3 protein is as known as MGC33488, LOC90326, and THAP domain-containing, apoptosis associated protein 3. This protein contains the Thanatos-associated protein (THAP) domain and a host-cell factor 1C binding motif. These domains allow THAP3 to influence a variety of processes, including transcription and neuronal development. THAP3 is ubiquitously expressed in H. sapiens, though expression is highest in the kidneys.
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