ABSTRACT
Mutations in AIPL1 cause Leber congenital amaurosis (LCA), the most severe form of inherited blindness in children; however, the function of this protein in normal vision remains unknown. To determine amino acid subsequences likely to be important for function, we have compared the protein sequence of several species. Sequence conservation is highest across the three Aipl1 tetratricopeptide (TPR) motifs and extends across the protein, except for a proline-rich amino acid sequence present only at the C-terminus of primate Aipl1. The length of the proline-rich region varies within primates; however, the length differences between human and primate Aipl1 do not correlate with evolutionary distance. These observations reinforce the importance of the TPR domains for function, the similarity of Aipl1 to a family of proteins that act as molecular chaperones, and the importance of comparative sequencing data for determination of whether AIPL1 sequence variants in patients are likely to cause retinopathy.
Subject(s)
Carrier Proteins/genetics , Optic Atrophies, Hereditary/genetics , Retinal Degeneration/genetics , Adaptor Proteins, Signal Transducing , Amino Acid Sequence , Animals , Blindness/genetics , Cattle , DNA Mutational Analysis , DNA Primers/chemistry , Eye Proteins , Humans , Macaca mulatta/genetics , Mice , Molecular Sequence Data , Mutation , Pan troglodytes/genetics , Papio/genetics , Phenotype , Phylogeny , Rats , Saimiri/genetics , Sequence Homology, Amino AcidABSTRACT
BACKGROUND: Activation of gastrin-releasing peptide receptor (GRPR) in human airways has been associated with a proliferative response of bronchial cells to gastrin-releasing peptide and with long-term tobacco use. The GRPR gene is located on the X chromosome and escapes X-chromosome inactivation, which occurs in females. Increasing evidence demonstrates that women are more susceptible than men to tobacco carcinogenesis. We hypothesized that the susceptibility of women to the effects of tobacco may be associated with airway expression of GRPR. METHODS: We analyzed GRPR messenger RNA (mRNA) expression in lung tissues and cultured airway cells from 78 individuals (40 males and 38 females) and in lung fibroblasts exposed to nicotine in vitro. Nicotinic acetylcholine receptors in airway cells were assayed by use of radioactively labeled nicotine and nicotine antagonists. A polymorphism in exon 2 of the GRPR gene was used to detect allele-specific GRPR mRNA expression in some individuals. Statistical tests were two-sided. RESULTS: GRPR mRNA expression was detected in airway cells and tissues of more female than male nonsmokers (55% versus 0%) and short-term smokers (1-25 pack-years [pack-years = number of packs of cigarettes smoked per day multiplied by the number of years of smoking]) (75% versus 20%) (P =.018 for nonsmoking and short-term smoking females versus nonsmoking and short-term smoking males). Female smokers exhibited expression of GRPR mRNA at a lower mean pack-year exposure than male smokers (37.4 pack-years versus 56.3 pack-years; P =.037). Lung fibroblasts and bronchial epithelial cells exhibited high-affinity, saturable nicotinic acetylcholine-binding sites. Expression of GRPR mRNA in lung fibroblasts was elevated following exposure to nicotine. CONCLUSIONS: Our results suggest that the GRPR gene is expressed more frequently in women than in men in the absence of smoking and that expression of this gene is activated earlier in women in response to tobacco exposure. The presence of two expressed copies of the GRPR gene in females may be a factor in the increased susceptibility of women to tobacco-induced lung cancer.
Subject(s)
Gene Expression Regulation, Neoplastic , Lung Neoplasms/etiology , Lung Neoplasms/metabolism , Receptors, Bombesin/metabolism , Respiratory System/metabolism , Smoking/adverse effects , Adult , Aged , Cells, Cultured , Female , Fibroblasts/drug effects , Fibroblasts/metabolism , Genotype , Humans , Lung/metabolism , Male , Middle Aged , Nicotine/adverse effects , Nicotine/metabolism , Polymorphism, Genetic , RNA Probes , RNA, Messenger/analysis , RNA, Neoplasm/analysis , Receptors, Bombesin/genetics , Respiratory System/cytology , Reverse Transcriptase Polymerase Chain Reaction , Risk , Sex Factors , Smoking/metabolismABSTRACT
Chromosome 3p is consistently deleted in lung cancer, oral squamous cell carcinoma, and renal cell carcinoma, and is believed to contain several tumor suppressor genes. We have shown a role for chromosome 3 in tumor suppression by microcell-mediated chromosome transfer experiments. We have isolated a gene that is located at 3p21.3 within the smallest region of deletion overlap in lung tumors and is the human homolog of the ribosomal protein L14 gene (RPL14). The RPL14 sequence contains a highly polymorphic trinucleotide repeat array which encodes a variable-length polyalanine tract. Genotype analysis of RPL14 shows that this locus is 68% heterozygous in the normal population, compared with 25% in non-small cell lung cancer (NSCLC) cell lines (p = 0.008). Cell cultures derived from normal bronchial epithelium show a 65% level of heterozygosity, reflecting that of the normal population. Squamous cell carcinoma of the head and neck (SCCHN), which has the same risk factors as lung cancer and is hypothesized to have a similar etiology, demonstrates 54% loss of heterozygosity at the RNA level, suggesting that transcriptional loss may be a primary mechanism of RPL14 alteration in SCCHN. In addition, RPL14 shows significant differences in allele frequency distribution in ethnically-defined populations, making this sequence a useful marker for the study of ethnicity-adjusted lung cancer risk.
