Tyrosinase activity and abundance in Cloudman melanoma cells

Halaban, Ruth; Pomerantz, Seymour H.; Marshall, Susan N.; Lerner, Aaron B.

doi:10.1016/0003-9861(84)90121-8

Cited by 105 publications

(66 citation statements)

References 18 publications

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“…Conversely, if the amount of enzyme is determined with a monoclonal antibody directed against the form present in higher amounts under basal conditions, little increase in the amount of enzyme will be observed, and the large increase in tyrosine hydroxylase activity due to the accumulation of a different isoenzyme not recognized by the antibody could be reasonably assigned to the activation of a preexisting pool of the enzyme [6]. Finally, if the specific activity is measured under conditions where the initial situation is such that both enzyme forms are already present in comparable amounts, for example after a previous aMSH stimulation, or if the antibody employed to determine tyrosinase amounts is mainly directed against the higher specific activity protein, the preferent stimulation of this form might lead to an interpretation of the results in terms of an aMSH induction without any activation of the enzyme [3,4]. In any case, a variety of experiments performed with specific antibodies have shown that czMSH treatment of melanocytes results in little differences in the patterns of sylathesis of both tyrosinases, which were increased no more than about two-fold by the hormone [16].…”

Section: Other Proceduresmentioning

confidence: 99%

“…However, the molecular mechanisms underlying tyrosinase induction are far from clear. It has been suggested that the effect of czMSH is not mediated by a change in the phosphorylation state of tyrosinase or in other post-translational modifications [2,3]. However, there is no agreement as to whether the increase in tyrosinase activity is mainly a function of enzyme abundance [3,4], or reflects both an increased amount of tyrosinase and an activation of previously existing molecules [5], or even the activation of an inactive enzyme pool with little, if any, effect on the rate of enzyme synthesis [6].…”

Section: I Introductionmentioning

confidence: 99%

“…It has been suggested that the effect of czMSH is not mediated by a change in the phosphorylation state of tyrosinase or in other post-translational modifications [2,3]. However, there is no agreement as to whether the increase in tyrosinase activity is mainly a function of enzyme abundance [3,4], or reflects both an increased amount of tyrosinase and an activation of previously existing molecules [5], or even the activation of an inactive enzyme pool with little, if any, effect on the rate of enzyme synthesis [6]. As far as the activation of pre-existing tyrosinase molecules is concerned, both the cAMP-mediated removal of an inhibitor [7] or synthesis of an activator [5] have been postulated, although no clear-cut evidence has ever been put forward.…”

Section: I Introductionmentioning

confidence: 99%

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Melanocyte stimulating hormone activation of tyrosinase in B16 mouse melanoma cells Evidence for a differential induction of two distinct isoenzymes

et al. 1992

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Tyrosinase induction in murine malignant melanoeytes by gMSH is well known, but its molecular basis has not been characterized. Treatment of BI6 melanoma cells with theophylline or rrMSH mediates a larger induction of tyrosine hydroxylase than of dopa oxidase activity in total cell extracts, and in the melanosomal and microsomal fractions. No evidence for the modulation of a tyrosinase effector was found. SDS-PAGE and slY~ific activity stain demonstrated two forms of tyro.,i~ase, with different degrees of induction by theophylline. These results agree with the recent proposal that two tyrosinases, encoded by different genes, are present in murine melanoeytes. cells in culture trigger the preferential expression of a tyrosinase isoenzyme different from the majority form found in untreated cells. Both forms differ in their electrophoretie mobility in non-reducing SDS-PAGE and in their catalytic properties. The isoenzyme preferentially induced by melanogenic agents displays a larger ratio of tyrosine hydroxylase to dopa oxidase activity, and would therefore mainly affect the first, rate limiting, step of the pathway. This finding conveniently accounts for most of the apparently controversial data in the literature. MATERIALS AND METHODS 2,1. Cell culture attd treatment with melanogenic effectorsBI6-F10 mouse melanoma cells were originally a kind gift of Dr. V. Hearing and have been maintained as described [8], BI6 melanocytes were culttared either on 96-well plates or in 75 cm: flasks from Nunc (Denmark). When using 9f-well plates, cells were seeded at a density of 5,000 ceils per well in 200/.tl of medium. After 24 h, serial dilutions of the melanogenie effectors were added in $0/,tl of medium, and the plate was further incubated for 48 h. Each concentration was assayed in six independent wells the contents of which were pooled by pairs before measurements so as to assay enzymatic activities in triplicate. To obtain higher amounts of cells for subcgllular fraetionation experiments. 5 • I0 S cells were sceclcd in 75 am" flasks, incubated for 24 h and then a volume of medium containing the desired con~ntra-lion of the melanogenic agent was added. Subcellular fractionattonCells were harvested by trypsin treatment and washed twice by centrifugation in homogenization buffer (HB, 10 mM phosphate pH 6.8, 0.25 M sucrose, 0.1 mM EDTA, 0.1 mM PMSF). The washed cells were suspended in HB at about I07 c.ll~'ml and disrupt,-d M a loosefitting, manual, glass-teflon homogenizer, at 4"C. A post-nuclear supernatant was obtained by centrifugation at 700 x g, and further 114Published by Elsevier Science Publishers B, K

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Section: Other Proceduresmentioning

confidence: 99%

Section: I Introductionmentioning

confidence: 99%

Section: I Introductionmentioning

confidence: 99%

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Melanocyte stimulating hormone activation of tyrosinase in B16 mouse melanoma cells Evidence for a differential induction of two distinct isoenzymes

et al. 1992

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“…These growth factors include several ®broblast growth factors (FGFs), hepatocyte growth factor or scatter factor (HGF/SF) and stem cell factor (SCF, also known as KIT-ligand, MGF and steel factor), all of which stimulate receptor tyrosine kinases. Since melanocyte proliferation and dierentiation are positively regulated by agents that increase cAMP (Halaban et al, 1983;1984;, we have focused on the transcription factor CREB (for CRE-binding protein) which is known to be activated by cAMP, as a possible mediator of tumor growth and metastasis of human melanoma cells.…”

Section: Introductionmentioning

confidence: 99%

Dominant-negative CREB inhibits tumor growth and metastasis of human melanoma cells

et al. 1997

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The ATF/CREB family of eukaryotic transcription factors contain the bZIP structural motif and mediate their transcriptional activities via heterodimerization with ATF and AP-1 family members. Quenching of CREBassociated proteins by a dominant-negative CREB (KCREB) that is mutated within its DNA-binding domain decreases radiation resistance of human melanoma cells. The purpose of this study was to determine the role of CREB in tumor growth and metastasis of human melanoma using KCREB. Highly metastatic MeWo human melanoma cells were transfected with the KCREB expression vector and subsequently analysed for changes in their tumorigenic and metastatic potential. Expression of KCREB in MeWo human cells decreased their tumorigenic and metastatic potential in nude mice compared with parental and control transfected cells. The KCREB-transfected cells displayed downregulation of 72 kDa collagenase type IV (MMP-2) mRNA expression and activity and decreased invasiveness through Matrigel-coated ®lters. Moreover, transcriptional activities mediated by the CAT gene driven by the MMP-2 promoter were decreased by 14 ± 45-fold in KCREB-transfected cells. In addition, the cell-surface adhesion molecule MCAM/MUC18 that is involved in metastasis of human melanoma was downregulated in the KCREB-transfected cells. These data indicate that, through their transcriptional activities, CREB and its associated proteins play an important role in the acquisition of the metastatic phenotype of human melanoma cells.

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“…Tyrosinase (monophenol, L-dopa:oxygen oxidoreductase, EC 1.14.18.1) is a bifunctional copper-containing glycoprotein that catalyzes the conversion first oftyrosine to dopa and then of dopa and dopaquinone in melanocytes (3,4). Recently, cDNAs encoding human (5,6) and mouse (7, 8) tyrosinase have been cloned, and the 528-amino acid sequence of the 58-kDA tyrosinase polypeptide (9) has been deduced.…”

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confidence: 99%

A frequent tyrosinase gene mutation in classic, tyrosinase-negative (type IA) oculocutaneous albinism.

Giebel

Strunk

King

et al. 1990

Proc. Natl. Acad. Sci. U.S.A.

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We have identified a tyrosinase gene mutation in several patients with classic, tyrosinase-negative (type IA) oculocutaneous albinism. This mutation, which results in a proline --leucine substitution at codon 81 of the tyrosinase polypeptide (EC 1.14.18.1), was observed in 20% (6 of 30) of oculocutaneous albinism alleles from independent probands, but it was not observed in any normal individuals. This mutation thus appears to be a frequent cause of tyrosinasenegative oculocutaneous albinism.

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Tyrosinase activity and abundance in Cloudman melanoma cells

Cited by 105 publications

References 18 publications

Melanocyte stimulating hormone activation of tyrosinase in B16 mouse melanoma cells Evidence for a differential induction of two distinct isoenzymes

Melanocyte stimulating hormone activation of tyrosinase in B16 mouse melanoma cells Evidence for a differential induction of two distinct isoenzymes

Dominant-negative CREB inhibits tumor growth and metastasis of human melanoma cells

A frequent tyrosinase gene mutation in classic, tyrosinase-negative (type IA) oculocutaneous albinism.

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