THE CARNITINE TRANSPORTER IN HUMAN DISEASE

描述(由申请人提供)：本项目的目标是描述肉碱转运体在人类疾病中的作用。肉碱将长链脂肪酸转移到线粒体膜上，以进行随后的β氧化。高亲和力OCTN2肉碱转运体的缺陷会导致原发性肉碱缺乏症，其特征是低酮症低血糖和/或骨骼/心肌病。随着肉碱转运部分受损的患者和肉碱转运蛋白基因有两个突变的成年患者(年龄24-37岁)完全没有症状，这种表型现在已经扩大到肉碱缺乏的症状。我们推测，这种表型变异可能是由于OCTN2的异常突变、其他肉碱转运蛋白的作用，或者是其他编码与OCTN2相互作用的蛋白或参与脂肪酸氧化的基因的影响。为了验证这一假设，我们将定义不寻常的OCTN2突变对功能的影响，评估其他肉碱转运体的活性和序列，定义与OCTN2肉碱转运体相互作用的蛋白质，并寻找不寻常形式的肉碱缺乏症患者的基因变化。将完成以下具体目标：目的1.研究肉碱缺乏症患者OCTN2肉碱转运体的突变。我们将排除已确定的突变可能的显性-负效应、与其他脂肪酸氧化基因突变的协同杂合性以及其他肉碱转运蛋白的变异。目的2.用双杂交系统鉴定与肉碱转运蛋白OCTN2相互作用的蛋白质。已确定的基因突变将在部分肉碱缺乏且肉碱转运体基因没有突变的有症状患者中寻找。这项研究将扩大肉碱缺乏的表型，阐明罕见形式的肉碱缺乏的分子基础，确定细胞内蛋白网络在膜转运体功能中的重要性，并确定微小的肉碱转运体在人类疾病中的可能作用。

DESCRIPTION (provided by applicant): The objective of this project is to characterize the role of carnitine transporters in human disease. Carnitine transfers long-chain fatty acids across the mitochondrial membrane for subsequent beta oxidation. A defect in the high-affinity OCTN2 carnitine transporter causes primary carnitine deficiency characterized by hypoketotic hypoglycemia and/or skeletal/cardiac myopathy. This phenotype has now expanded with the identification of symptoms of carnitine deficiency in patients with only partially impaired carnitine transport and adult patients (age 24-37) with 2 mutations in the carnitine transporter gene completely asymptomatic. We hypothesize that this phenotypic variability can be due to unusual OCTN2 mutations, to the contribution of other carnitine transporters, or to the effect of other genes encoding proteins interacting with OCTN2 or involved in fatty acid oxidation. To test this hypothesis, we will define the effect on function of unusual OCTN2 mutations, evaluate activity and sequence of other carnitine transporters, define proteins interacting with the OCTN2 carnitine transporter and look for alterations in their genes in patients with unusual forms of carnitine deficiency. The following specific aims will be accomplished: Aim 1. Study mutations in the OCTN2 carnitine transporter of patients with unusual phenotype of carnitine deficiency. We will exclude a possible dominant-negative effect of the mutation identified, synergistic heterozygosity with mutations in other fatty acid oxidation genes and variations in other carnitine transporters. Aim 2. Identification of proteins interacting with the carnitine transporter OCTN2 using the 2-hybrid system. Mutations in the genes identified will be sought in symptomatic patients with partial carnitine deficiency and no mutations in the carnitine transporter gene. This study will expand the phenotype of carnitine deficiency, clarify the molecular basis of unusual forms of carnitine deficiency, define the importance of intracellular protein networks in the functioning of membrane transporters, and identify the possible role of minor carnitine transporters in human disease.