Gwinn M R, Sharma A, De Nardin E
Department of Oral Biology, State University of New York, Buffalo, USA.
J Periodontol. 1999 Oct;70(10):1194-201. doi: 10.1902/jop.1999.70.10.1194.
Neutrophils from patients with localized juvenile periodontitis (LJP) exhibit decreased binding and responsiveness to various chemotactic agents, including N-formyl-1-methionyl-1-leucyl-1-phenylalanine (FMLP). This altered reaction of neutrophils is thought to account in part for the increased susceptibility of LJP patients to infections by periodontal organisms. Receptors for FMLP are involved in the activation and the subsequent response to certain chemotactic stimuli.
In order to determine if this decreased response is due to a genetic variation in the receptor, we directly compared DNA encoding the FMLP receptor from controls matched for gender and race and LJP patients by single-strand conformation polymorphism analysis (SSCP).
Using this technique, we observed a characteristic SSCP pattern in 29 out of 30 patient samples in the FMLP receptor DNA. This pattern differed from those obtained from the 20 control subjects as well as 31 patients with adult periodontitis. DNA sequencing of 30 patients indicated single nucleotide polymorphisms (SNPs) in the FMLP receptor DNA from the LJP patients when compared to 20 controls (P = 0.0005). Two single nucleotide base alterations were consistently seen: either a thymine to cytosine substitution at base 329 in 17 LJP patients or a cytosine to guanine substitution at base 378 in 5 LJP patients. A combination of both alterations were seen in 7 LJP patients. Both alterations resulted in amino acid changes in the second intracellular loop of the receptor, specifically phenylalanine to serine at residue 110 and cysteine to tryptophan at residue 126. This region of the FMLP receptor has recently been shown to play a role in ligand binding and G-protein activation.
This study suggests that a molecular alteration in the second intracellular loop of the FMLP receptor molecules in LP patients may play a role in the decreased chemotactic activity reported for some LJP patients.
局限性青少年牙周炎（LJP）患者的中性粒细胞对包括N-甲酰-1-蛋氨酰-1-亮氨酰-1-苯丙氨酸（FMLP）在内的多种趋化剂的结合和反应性降低。中性粒细胞的这种反应改变被认为部分解释了LJP患者对牙周微生物感染易感性增加的原因。FMLP受体参与对某些趋化刺激的激活及随后的反应。
为了确定这种反应降低是否由于受体的基因变异，我们通过单链构象多态性分析（SSCP）直接比较了性别和种族匹配的对照组以及LJP患者中编码FMLP受体的DNA。
使用该技术，我们在30例患者样本中的29例FMLP受体DNA中观察到一种特征性的SSCP模式。这种模式不同于从20例对照受试者以及31例成人牙周炎患者中获得的模式。对30例患者的DNA测序表明，与20例对照相比，LJP患者的FMLP受体DNA中存在单核苷酸多态性（SNP）（P = 0.0005）。始终可见两种单核苷酸碱基改变：17例LJP患者中第329位碱基由胸腺嘧啶替换为胞嘧啶，或5例LJP患者中第378位碱基由胞嘧啶替换为鸟嘌呤。7例LJP患者中同时出现了两种改变。两种改变均导致受体第二个细胞内环中的氨基酸变化，具体为第110位残基处的苯丙氨酸变为丝氨酸，第本126位残基处的半胱氨酸变为色氨酸。最近已表明FMLP受体的该区域在配体结合和G蛋白激活中起作用。
本研究表明，LJP患者FMLP受体分子第二个细胞内环中的分子改变可能在一些LJP患者报道的趋化活性降低中起作用。
