Bennett T A, Edwards B S, Sklar L A, Rogelj S
Department of Pathology, Division of Cytometry, Cancer Research Facility, University of New Mexico School of Medicine, Albuquerque, NM 87131, USA.
J Immunol. 2000 Apr 15;164(8):4120-9. doi: 10.4049/jimmunol.164.8.4120.
The L-selectin adhesion molecule mediates leukocyte recruitment to inflammatory sites and lymphocyte trafficking through the peripheral lymph nodes. In response to leukocyte activation, L-selectin is proteolytically released from the cell surface, disabling leukocytes from the subsequent L-selectin-dependent interactions. We have found that L-selectin shedding is sensitive to sulfhydryl chemistry; it is promoted by thiol-oxidizing or -blocking reagents and inhibited by reducing reagents. Phenylarsine oxide (PAO), a trivalent arsenical that interacts with vicinal dithiols, is most potent in inducing rapid shedding of L-selectin from isolated neutrophils, eosinophils, and lymphocytes as well as from neutrophils in whole blood. PAO does not cause cell activation, nor does it interfere with integrin function or alter the expression of several other cell surface molecules at the low concentrations that induce L-selectin shedding. PAO is not required to enter the cell to induce L-selectin shedding. TAPI-2 ((N-(D,L-[2-(hydroxyaminocarbonyl)-methyl]-4-methylpentanoyl)-L-3-(tert-butyl)-alanyl-l -alanine, 2-aminoethyl amide), which has previously been shown to inhibit the activation-dependent L-selectin shedding, is also capable of inhibiting PAO-induced L-selectin shedding. We hypothesize that PAO-induced L-selectin shedding involves a regulatory molecule, such as protein disulfide isomerase (PDI), an enzyme that plays a role in the formation and rearrangement of disulfide bonds, contains PAO-binding, vicinal dithiol-active sites, and is expressed on the neutrophil surface. Cell surface expression of PDI, L-selectin shedding induced by PDI-blocking Abs and by bacitracin, a known inhibitor of PDI activity, and direct binding of PDI to PAO, provide supporting evidence for this hypothesis.
L-选择素黏附分子介导白细胞募集至炎症部位以及淋巴细胞通过外周淋巴结的迁移。响应白细胞激活时，L-选择素从细胞表面被蛋白水解释放，使白细胞无法进行随后依赖L-选择素的相互作用。我们发现L-选择素的脱落对巯基化学敏感；它由硫醇氧化或阻断试剂促进，并由还原试剂抑制。苯胂酸氧化物（PAO），一种与邻二硫醇相互作用的三价砷化合物，在诱导L-选择素从分离的中性粒细胞、嗜酸性粒细胞和淋巴细胞以及全血中的中性粒细胞快速脱落方面最为有效。PAO不会引起细胞激活，在诱导L-选择素脱落的低浓度下也不会干扰整合素功能或改变其他几种细胞表面分子的表达。PAO诱导L-选择素脱落不需要进入细胞。TAPI-2（N-(D,L-[2-(羟基氨基羰基)-甲基]-4-甲基戊酰基)-L-3-(叔丁基)-丙氨酰-L-丙氨酸，2-氨基乙酰胺），先前已被证明可抑制依赖激活的L-选择素脱落，也能够抑制PAO诱导的L-选择素脱落。我们推测PAO诱导的L-选择素脱落涉及一种调节分子，如蛋白二硫键异构酶（PDI），一种在二硫键形成和重排中起作用、含有PAO结合的邻二硫醇活性位点且在中性粒细胞表面表达的酶。PDI的细胞表面表达、由PDI阻断抗体和杆菌肽（一种已知的PDI活性抑制剂）诱导的L-选择素脱落以及PDI与PAO的直接结合，为这一推测提供了支持证据。
