Role of ADAM8 in experimental asthma

A disintegrin and metalloprotease (ADAM) family members, characterized by a metalloprotease and a disintegrin domain, are membrane-anchored glycoproteins involved in proteolysis and cell adhesion. ADAM8 is specifically induced in the experimental murine asthmatic lung. To evaluate novel pathways involved in asthma pathogenesis, using ADAM8 transgenic mice (ATMS2) in a murine model of asthma. Massive cellular infiltrates in peribronchovascular and interstitial lesions were observed in control mice, while in ATMS2 mice there were only occasional. Vascular cell adhesion molecule (VCAM-1) is involved in specific eosinophil adhesions via alpha4beta1 integrin. VCAM-1 shedding was mediated by the ADAM8 metalloprotease. Endothelial cell shedding of VCAM-1 was increased in ATMS2-stimulated human umbilical endothelial cells. ADAM8-mediated shedding of VCAM-1 might be important for the suppression of experimental asthma. Our data suggest that ADAM8 is a useful therapeutic target.     

解聚素与金属蛋白酶10功能研究进展

解聚素与金属蛋白酶10(ADAM10)是细胞膜上一种重要的调节分子.它通过调节性膜内蛋白水解(regulated intramembrane proteolysis),引起底物分子的胞外功能区的脱落,释放各种生长因子,或者调节细胞内的蛋白水解,进一步启动细胞内的信号转导途径.ADAM10通过这种方式参与了中枢神经系统的发育和生长、炎症反应以及肿瘤的形成和侵袭.本文仅就ADAM10的分子结构,4类主要的作用底物和发挥的功能作一简要介绍.     

Elevation of serum soluble vascular cell adhesion molecule-1 (sVCAM-1) levels in bronchial asthma.

We have previously shown the elevation of serum soluble intercellular adhesion molecule-1 (sICAM-1) and soluble E-selectin (sE-selectin) in patients with bronchial asthma during asthma attacks. In the present study, we extended our earlier study by measuring serum sVCAM-1 levels by ELISA in 45 patients with bronchial asthma (23 atopic and 22 non-atopic) during asthma attacks and in stable conditions in order to assess further the state of adhesion molecules in allergic inflammation of bronchial asthma. The levels of sVCAM-1 in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. These findings were observed regardless of atopic status. To examine the regulatory mechanism in the elevation of serum sVCAM-1 levels, serum tumor necrosis factor-alpha (TNF-alpha) levels were measured by ELISA. TNF-alpha levels in sera obtained during bronchial asthma attacks were higher than those in sera obtained in stable conditions. The nature of change in serum TNF-alpha levels correlated with the nature of change in serum sVCAM-1 levels, but serum TNF-alpha levels did not correlate with serum sVCAM-1 levels. These results suggest that higher levels of sVCAM-1 during asthma attacks may reflect the up-regulation of VCAM-1 expression in allergic inflammation, and that a soluble form of VCAM-1 molecules may be useful markers for the presence of allergic inflammation. TNF-alpha is shown to enhance the expression and release of VCAM-1 in vitro, however; the regulatory mechanism in the elevation of serum sVCAM-1 levels remains to be clarified.     

Accumulation of CXCR3-expressing eosinophils and increased concentration of its ligands (IP10 and Mig) in bronchoalveolar lavage fluid of patients with chronic eosinophilic pneumonia

BACKGROUND: Since human peripheral eosinophils have been shown to migrate to the CXC chemokine receptor 3 (CXCR3) ligands IFN-gamma-inducible protein 10 (IP10) and monokine induced by IFN-gamma (Mig), this confirms that CXCR3 is functionally expressed on these cells. IP10 expression has been shown to be increased in the airways of asthmatics. Eosinophil accumulations are found in bronchoalveolar lavage fluid (BALF) from patients with chronic eosinophilic pneumonia (CEP). To examine the contribution of IP10 and Mig in the pathogenesis of CEP, we measured the concentration of IP10 and Mig, and evaluated the expression of CXCR3 on eosinophils in BALF taken from patients with CEP. METHODS: The concentrations of IP10 and Mig in BALF were measured by ELISA. The proportion of CXCR3-expressing CD4+ T cells and CD16-negative eosinophils was determined by flow cytometry. RESULTS: The BALF concentrations of IP10 and Mig were higher in patients with CEP, as well as in patients with sarcoidosis, when compared to healthy controls. The absolute number of CXCR3+ CD4+ T cells was significantly higher in the BALF of patients with sarcoidosis, but not in the patients with CEP, when compared to healthy volunteers. There were higher percentages of CXCR3-expressing eosinophils in the BALF than in the peripheral blood of patients with CEP. CONCLUSIONS: Our findings suggest that IP10 and Mig contribute to the accumulation of CXCR3-expressing eosinophils in the lungs of patients with CEP, and modulate the eosinophilic inflammation of the lung.     

Metalloprotease-disintegrin ADAM8: expression analysis and targeted deletion in mice.

ADAM8 (a disintegrin and metalloprotease 8, also referred to as MS2/CD156a) is a membrane-anchored metalloprotease that was first identified in a macrophage cell line and has been implicated in neurodegenerative diseases. Here, we evaluated the expression of ADAM8 during mouse development and generated mice lacking ADAM8 (Adam8-/- mice). During early mouse development, ADAM8 is expressed by maternal cells in the decidua and by trophoblast derivatives of the embryo but not in the derivatives of the inner cell mass. At later stages, prominent expression of ADAM8 is seen in the embryo proper, in the gonadal ridge, thymus, developing cartilage and bone, brain and spinal cord, and in the mesenchyme in close proximity to the branch point between the jugular vein and developing lymphatic vessels. Examination of Adam8-/- mice, however, revealed no major defects in these or other structures during development or in adult tissues and no evident pathological phenotypes.     

ADAM family proteins in the immune system.

CD156 is a member of a family proteins characterized by a disintegrin and a metalloprotease domain (ADAM). These molecules are phylogenically conserved but have individual roles in a variety of cells. Here, Shunsuke Yamamoto and colleagues discuss data suggesting that ADAM family proteins have important roles in the immune system.     

The detection of ADAM8 protein on cells of the human immune system and the demonstration of its expression on peripheral blood B cells, dendritic cells and monocyte subsets

A disintegrin and metalloprotease (ADAM) proteins have wide ranging functions, including proteolytic cleavage of cell surface molecules, cell fusion, cell adhesion and intracellular signalling. Recent evidence suggests the involvement of ADAM8 in allergic responses. For instance, ADAM8 is amongst a number of genes up-regulated in experimentally induced asthma in animals. In order to further define the involvement of ADAM8 in allergic responses, we sought in the first instance to examine its distribution on human peripheral blood B cells, resting and activated T cells, monocyte subsets and monocyte derived dendritic cells. Here we demonstrate for the first time ADAM8 protein expression on B cells and dendritic cells, and its higher expression on CD14(2+)CD16(-) monocytes compared to CD14(+)CD16(+) cells. Immature dendritic cells expressed low levels of ADAM8 when treated with a combination of GM-CSF and IL-4, but stimulation with LPS resulted in a higher level of expression, which was TLR-4 independent. Up-regulation of ADAM8 expression on dendritic cells was also observed after stimulation with TNF-alpha, but not after stimulation with anti-CD40. The demonstration of ADAM8 expression on these cells provides an opportunity for addressing the potential role of inhaled protease allergens, such as Der p 1, in modulating ADAM8 functions, particularly with regards to innate immune responses by dendritic cells and IgE synthesis by B cells.     

The expression of ADAM23 and its correlation with promoter methylation in non-small-cell lung carcinoma

ADAM23, a member of a disintegrin and metalloprotease (ADAM) family, has been reported to be expressed in several types of tumours. The exact role of ADAM23 and the possible mechanisms in which it is involved in non-small-cell lung carcinoma (NSCLC) remains unclear. Therefore, this study was designed to explore the expression of ADAM23 and its correlation with promoter methylation in NSCLC. Immunohistochemistry and RT-PCR together with Western blotting methods were used to analyse the expression of ADAM23 in 52 cancer tissue samples and eight benign pulmonary lesions as well as four cell lines. The methylated status of ADAM23 gene was determined with methylation-specific PCR (MSP). The results of immunohistochemistry showed that the expression of ADAM23 protein was lower in NSCLC than that in corresponding normal tissues and benign pulmonary lesions (38.5%vs. 86.5% and 87.5%, P < 0.05), and decreased as NSCLC progressed. Meanwhile, methylation of ADAM23 gene was observed in 21 of 52 NSCLC tissues (40.4%), much higher than that of adjacent normal tissues (7.6%) and benign pulmonary lesions (0/8). In the cancer tissues of ADAM23-negative samples, the rate of ADAM23 gene methylation was 50.3% (17/32). ADAM23 expression and its promoter methylation were negatively associated (r = -0.328, P = 0.017). Moreover, weak expression of ADAM23 in methylated cancer cells increased after treatment with 5-aza-2'-deoxycytidine (5-Aza-2'-dC), confirming that methylation was responsible for the gene downregulation. Our results demonstrate that the expression level of ADAM23 is likely to be involved in the progression of NSCLC and its downregulation is probably correlated with promoter methylation. These findings may provide potential diagnostic and prognostic information about NSCLC.     

The effects of Th2 cytokines on the expression of ADAM33 in allergen-induced chronic airway inflammation

A disintegrin and metalloprotease domain 33 (ADAM33) has been identified as an asthma susceptibility gene, which is associated with small-airway remodeling. However, the role of ADAM33 in the development of allergic airway inflammation is unclear. The present study used an established murine model of allergen-induced chronic airway inflammation, which was sensitized and then challenged by nebulized 2.5% ovalbumin (OVA) for 8 weeks (30 min/day, three times a week). The expression of ADAM33 mRNA detected by real time RT-PCR was significantly enhanced in the lung tissue of mice with OVA challenge, as compared with the group challenged with saline. This OVA-challenged model showed significant Th2-biased airway inflammation as well as airway remodeling with features of sub-epithelial fibrosis and mucus hyper-secretion. Furthermore, in vitro studies showed that IL-4 and IL-13 could significantly up-regulate the expression of ADAM33 mRNA in human fibroblasts in a concentration- and time-dependent manner as compared to normal controls. These results support the note that Th2 cytokines can up-regulate the expression of ADAM33 mRNA and ADAM33 may play an important role in the development of airway remodeling in allergen-induced chronic airway inflammation.     

Triggering through CD40 promotes interleukin-4-induced CD23 production and enhanced soluble CD23 release in atopic disease

The pathogenesis of atopic disease is closely linked to the overproduction of IgE. CD23 and CD40 are two cellular receptors involved in the regulation of IgE production and both receptors are elevated in atopic disease. We have examined the role of CD40 in the regulation of CD23 and soluble CD23 production in healthy and atopic donors. Triggering of the B cell CD40 receptor directly enhances interleukin (IL)-4-mediated up-regulation of CD23 at both the protein and the mRNA level. When atopic donors were studied, the synergistic effect of CD40 triggering on the IL-4-induced up-regulation of CD23 and soluble CD23 (sCD23) was enhanced and there was a relative skewing toward production of sCD23. These studies implicate the CD40 receptor in the hyperproduction of CD23 and sCD23 in atopic disease and suggest that abnormalities may exist in the cellular pathways leading to sCD23 production.     

Elevated interleukin-18 levels in bronchoalveolar lavage fluid of patients with eosinophilic pneumonia

BACKGROUND: Interleukin (IL)-18 can induce Th2 cytokine production particularly in collaboration with IL-2. Accumulation of Th2 cells and increased levels of Th2 cytokines are found in bronchoalveolar lavage fluid (BALF) from patients with eosinophilic pneumonia (EP). To evaluate the role of IL-18 in the pathogenesis of EP, we measured the concentration of IL-2, IL-12, IL-18, and Th2 cytokines in BALF from patients with EP. METHODS: The concentrations of interferon (IFN)-gamma, IL-2, IL-5, IL-10, IL-12, IL-13, and IL-18 in BALF were measured in patients with idiopathic acute eosinophilic pneumonia (AEP), with idiopathic chronic eosinophilic pneumonia (CEP), with sarcoidosis and healthy volunteers (HV). RESULTS: The BALF concentrations of Th2 cytokines, IL-5, IL-10, and IL-13, were higher in patients with EP than in sarcoidosis and control. The IL-2 level in BALF was higher in EP than in sarcoidosis and control. The IL-18 and IL-12 (p40 + p70) levels were higher in patients with EP than sarcoidosis, while the level of IL-12 (p70) was below the detection limit in patients with EP. There was a significant correlation between IL-2 level and both IL-5 and IL-13 in BALF of patients with EP. CONCLUSIONS: Our findings suggest that IL-18 may contribute to Th2 cytokine-dominant responses in patients with EP in collaboration with IL-2.     

Expression of IL-18 mRNA and secretion of IL-18 are reduced in monocytes from patients with atopic dermatitis

BACKGROUND: Nasal polyps (NPs) are characterized by eosinophilic inflammation and often coexist with asthma. However, the role of atopy and IgE in NP pathogenesis is unclear. OBJECTIVE: We sought to determine whether there is an association between total and specific IgE to a variety of allergens in polyp and nonpolyp tissue and markers of eosinophilic inflammation or skin test results. METHODS: Homogenates were prepared from nasal tissue of 20 patients with NPs and 20 patients without NPs and analyzed for concentrations of IL-5, IL-4, eotaxin, leukotriene (LT) C4/D4/E4, sCD23, and histamine (ELISA). Eosinophil cationic protein (ECP), tryptase, and total and specific IgE for inhalant allergens and Staphylococcus aureus enterotoxins were measured (ImmunoCAP). RESULTS: The concentrations of total IgE, IL-5, eotaxin, ECP, LTC4/D4/E4, and sCD23 were significantly higher in NP tissue compared with nonpolyp tissue. Total IgE was significantly correlated to IL-5, ECP, LTC4/D4/E4, and sCD23 and to the number of eosinophils in NPs. On the basis of the presence of specific IgE antibodies in tissue, 3 NP groups were defined. NP group 1 demonstrated no measurable specific IgE, and NP group 2 selected specific IgE. The third group demonstrated a multiclonal specific IgE, including IgE to S aureus enterotoxins, a high total IgE level, and a high prevalence of asthma. CONCLUSIONS: These studies suggest that there is an association between increased levels of total IgE, specific IgE, and eosinophilic inflammation in NPs, which may be of relevance in the pathophysiology of nasal polyposis. Similarly, the presence of specific IgE to staphylococcal enterotoxins A and B also points to a possible role of bacterial superantigens.     

Association of a disintegrin and metalloprotease 33 (ADAM33) gene with asthma in ethnically diverse populations

BACKGROUND: Asthma is a complex genetic disease characterized by reversible intermittent airway obstruction and respiratory symptoms primarily caused by acute and chronic bronchial inflammation. Recently, a gene potentially involved in airway remodeling, a disintegrin and metalloprotease 33 (ADAM33), was implicated in asthma susceptibility. OBJECTIVE: We sought to determine whether polymorphisms in ADAM33 are associated with asthma or closely related phenotypes in 4 different asthma populations. METHODS: Eight single nucleotide polymorphisms (SNPs) were evaluated in the 3' portion of ADAM33 in 4 unique asthma populations (African American, US white, US Hispanic, and Dutch white). These SNPs were previously reported to be associated with asthma in white populations from the United States and United Kingdom. RESULTS: Significant associations were observed with at least one SNP and asthma in each population (P =.0009-.04). Related phenotypes that included total serum IgE levels and skin test responsiveness were also associated (P =.003-.05). However, no single SNP was associated across all populations. Additionally, haplotype analysis revealed that no single haplotype accounted for asthma susceptibility risk, although potential risk haplotypes existed within some of the populations. CONCLUSION: Replication of the original ADAM33 findings in these 4 additional asthma populations suggests that this gene (and perhaps others that interact with it) is important in the development and pathogenesis of asthma.     

Expression of seven members of the ADAM family in developing chicken spinal cord

The expression patterns of seven members of the ADAM (a disintegrin and metalloprotease) family, including ADAM9, ADAM10, ADAM12, ADAM13, ADAM17, ADAM22, and ADAM23, were analyzed in the developing chicken lumbar spinal cord by in situ hybridization and immunohistochemistry. Results show that each individual ADAM is expressed and regulated spatiotemporally in the lumbar cord and its surrounding tissues. ADAM9, ADAM10, ADAM22, and ADAM23 are expressed predominantly by motoneurons in the motor column and by sensory neurons in the dorsal root ganglia, each with a different expression pattern. ADAM12 and ADAM13 are mainly expressed in the meninges around the lumbar cord and in the condensed sheets of chondroblasts around the vertebrae. ADAM17 expression is strong in the ventricular layer and limited to early stages. The differential expression of the ADAMs in the lumbar cord suggests that the ADAMs play a regulatory role in development of the spinal cord. Developmental Dynamics 239:1246–1254, 2010. © 2010 Wiley‐Liss, Inc.     

Soluble endothelium-associated adhesion molecules in patients with Graves' disease.

The targeting and recruitment of inflammatory cells to vascular endothelium in Graves' disease (GD) is mediated by intercellular adhesion molecule-1 (ICAM-1), endothelial leucocyte adhesion molecule-1 (ELAM-1), and vascular cell adhesion molecule-1 (VCAM-1). We have studied serum levels of soluble ICAM-1 (sICAM-1), soluble ELAM-1 (sELAM-1), and soluble VCAM-1 (sVCAM-1) in patients with GD (n = 21) and in patients with iodine-deficient goitre (IDG) (n = 23). The serum levels of sICAM-1 were markedly elevated in patients with GD before treatment with thiamazole (median 560 ng/ml versus 185 ng/ml in patients with IDG). In addition, elevated serum concentrations of sELAM-1 (median 85 ng/ml versus 33 ng/ml, respectively) and sVCAM-1 (median 42 ng/ml versus 15 ng/ml, respectively) were observed in patients with GD (P < 0.01 for all). The serum levels of sELAM-1 and sVCAM-1 dropped significantly after initiation of therapy and were within the normal range after 4, and 8 weeks of therapy, respectively. Serum levels of sICAM-1 were elevated even after 8 weeks of therapy. Serum levels of sVACM-1 and sICAM-1 correlated with the serum concentrations of anti-thyroid-stimulating hormone (TSH)-receptor antibodies (TSHR-R) (n = 21; r = 0.929 and r = 0.810, respectively) and anti-thyroid peroxidase antibodies (TPO-Ab) (n = 21; r = 0.673 and r = 0.750, respectively). However, no correlation between sELAM-1 and TPO-Ab, TSHR-R, and anti-thyroglobulin antibodies (Tg-Ab), respectively, could be found. In addition to thyroid hormones and autoantibodies, serum concentrations of sELAM-1 and sVCAM-1, but not sICAM-1, could be useful as clinical markers for disease activity.     

Novel metalloprotease-disintegrin, meltrin epsilon (ADAM35), expressed in epithelial tissues during chick embryogenesis.

Members of the ADAM (a disintegrin and metalloprotease) family are involved in fertilization, morphogenesis, and pathogenesis. Their metalloprotease domains mediate limited proteolysis, including ectodomain shedding of membrane-anchored growth factors and intercellular-signaling proteins, and their disintegrin domains play regulatory roles in cell adhesion and migration. In screening for cDNAs encoding chicken ADAM proteins expressed during muscle development, we identified Meltrin epsilon as a novel member of this family. To elucidate its functions, we investigated its expression during development by using antibodies raised against its protease domain. In the somites, Meltrin epsilon protein was specifically expressed in the myotomal cells, which delaminate from the dermomyotome to form epithelial sheets. It was also found in the surface ectoderm, lens placodes, otic vesicles, and the gut epithelia. Basolateral localization of Meltrin epsilon in these epithelial cells suggests its unique roles in the organization of the epithelial tissues and development of the sensory organs and the gut.     

Increased expression of soluble form of vascular cell adhesion molecule-1 aggravates autoimmune arthritis in MRL-Fas(lpr) mice

Vascular cell adhesion molecule-1 (VCAM-1, CD106) is important in leukocyte trafficking and its increased expression is associated with a number of chronic inflammatory diseases, including rheumatoid arthritis (RA). A soluble form of VCAM-1 (sVCAM-1) is generated by shedding of the membrane-bound molecule. The concentration of sVCAM-1 is increased in the sera of RA patients, but its pathological role has not been elucidated. The effect of sVCAM-1 relative to protection or aggravation of disease on the development of spontaneous arthritis was examined in an animal model of RA, namely MRL-Fas(lpr) mice (which display a disease resembling human RA), by generation of sVCAM-1 transgenic MRL-Fas(lpr) mice. Transgenic MRL-Fas(lpr) mice that expressed sVCAM-1 had higher incidence and increased severity of arthritis associated with higher levels of serum IgG rheumatoid factor compared with non-transgenic MRL-Fas(lpr) mice. These results suggest that sVCAM-1 plays an arthritogenic role in the development of inflammatory arthritis in MRL-Fas(lpr) mice and may present an important target for therapeutic strategy of RA.     

Regional expression of the ADAMs in developing chicken cochlea

The expression patterns of five members of the ADAM (a disintegrin and metalloprotease) family including ADAM9, ADAM10, ADAM17, ADAM22, and ADAM23 were analyzed in different anatomical structures of the developing chicken cochlea by in situ hybridization and immunohistochemistry. Results show that ADAM9, ADAM10, and ADAM17 are widely expressed in the sensory epithelium of the basilar papilla, by homogene cells, spindle‐shaped cells, and acoustic ganglion cells, and in the tegmentum vasculosum, each with a different pattern. ADAM22 expression is restricted to spindle‐shaped cells and acoustic ganglion cells, while ADAM23 is prominently expressed by hair cells and acoustic ganglion cells. Furthermore, ADAM10 protein is coexpressed with several members of the classic cadherins, including cadherin‐7, N‐cadherin, and R‐cadherin in distinct anatomical regions of the cochlea except for acoustic ganglion cells. The expression of the ADAMs in the developing cochlea suggests a contribution of the ADAMs to the development of distinct cochlear structures. Developmental Dynamics 239:2256–2265, 2010. © 2010 Wiley‐Liss, Inc.     

Cutaneous CD30+ cells in children with atopic dermatitis

BACKGROUND: CD30 expression can be considered a marker of Th2 cells. We investigated the presence of CD30+ cells in the lesional skin of children with atopic dermatitis (AD). We also analyzed the possible relationship between CD30+ cells and serum soluble CD 30 (sCD30) levels, and IgE, soluble interleukin-2 (IL-2) receptor (sIL-2R) or soluble CD23 (sCD23) levels in the blood, and clinical score. METHODS: Ten eczematous children (4 males, 6 females; median age: 4 years and 5 months; range: 11 months to 14 years), 9 sex- and age-matched control children and an adult control group were studied. A clinical score (SCORAD index), was given to eczematous lesions. Blood was taken for the determination of IgE, sCD30, sIL-2R and sCD23 levels. Punch biopsies of lesional skin were stained with hematoxylin and eosin or incubated with anti-CD30 monoclonal antibodies. Skin prick tests (SPTs) were also performed. RESULTS: In the biopsy specimens, CD30 expression was observed in high proportions of infiltrating cells. In children with AD, total serum IgE, sCD30, sIL-2R, sCD23 and eosinophils were significantly elevated compared to controls. CD30+ cells were not associated with serum IgE, sCD30, sIL-2R, sCD23, or SPT results, score of inflammatory cells in lesional skin or clinical score. Children with AD who had high total IgE and specific IgE antibodies did not differ from those with normal total IgE and negative specific IgE in respect of age, clinical score, number of CD30+ cells, sCD30, sIL-2R and sCD23 levels, score of inflammatory cells in skin or clinical score. CONCLUSION: Our results showed remarkable numbers of CD30+ cells in the lesional skin and high sCD30 in the serum of children with AD. CD30+ cells did not correlate with systemic markers of IgE reaction.     

Meltrin beta (ADAM19) mediates ectodomain shedding of Neuregulin beta1 in the Golgi apparatus: fluorescence correlation spectroscopic observation of the dynamics of ectodomain shedding in living cells

Membrane-anchored Neuregulin beta1 sheds its ectodomain as soluble factors. Two proteases that belong to a disintegrin and metalloprotease (ADAM) family are known to cleave Neuregulin beta1. One is tumor necrosis factor-alpha converting enzyme (TACE/ADAM17). The other is Meltrin beta (ADAM19). Against our expectation that shedding by ADAM proteases occurs at the cell surface, here we found that Meltrin beta mediates the ectodomain shedding of Neuregulin beta1 in the Golgi apparatus. Meltrin beta was localized in and around the Golgi apparatus in developing sensory neurons. Subcellular fractionation revealed that Meltrin beta generated soluble Neuregulin beta1 in Golgi-enriched fractions while TACE-cleaved Neuregulin beta1 was recovered in lighter fractions. To examine whether Meltrin beta-mediated ectodomain shedding occurs in the Golgi apparatus in living cells, we took advantage of different diffusion properties of cleavage products from those of membrane-anchored precursor proteins. Fluorescence correlation spectroscopy (FCS) is the most sensitive method to determine milli approximately submillisecond diffusion in vivo. Protease-active Meltrin beta caused a shift in autocorrelation function in FCS of green fluorescent protein (GFP)-tagged Neuregulin beta1 in the Golgi apparatus, suggesting a conversion of Neuregulin beta1 molecules from membrane-anchored to soluble forms in that organelle. The Golgi apparatus is a site of processing Neuregulin beta1 by Meltrin beta.