Dataset Information

Proprotein convertases process Pmel17 during secretion.

ABSTRACT: Pmel17 is a melanocyte/melanoma-specific protein that traffics to melanosomes where it forms a fibrillar matrix on which melanin gets deposited. Before being cleaved into smaller fibrillogenic fragments the protein undergoes processing by proprotein convertases, a class of serine proteases that typically recognize the canonical motif RX(R/K)R?. The current model of Pmel17 maturation states that this processing step occurs in melanosomes, but in light of recent reports this issue has become controversial. We therefore addressed this question by thoroughly assessing the processing kinetics of either wild-type Pmel17 or a secreted soluble Pmel17 derivative. Our results demonstrate clearly that processing of Pmel17 occurs during secretion and that it does not require entry of the protein into the endocytic system. Strikingly, processing proceeds even in the presence of the secretion inhibitor monensin, suggesting that Pmel17 is an exceptionally good substrate. In line with this, we find that newly synthesized surface Pmel17 is already quantitatively cleaved. Moreover, we demonstrate that Pmel17 function is independent of the sequence identity of its unconventional proprotein convertase-cleavage motif that lacks arginine in P4 position. The data alter the current view of Pmel17 maturation and suggest that the multistep processing of Pmel17 begins with an early cleavage during secretion that primes the protein for later functional processing.

SUBMITTER: Leonhardt RM

PROVIDER: S-EPMC3059051 | biostudies-other | 2011 Mar

REPOSITORIES: biostudies-other

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Proprotein convertases process Pmel17 during secretion.

Leonhardt Ralf M RM Vigneron Nathalie N Rahner Christoph C Cresswell Peter P

The Journal of biological chemistry 20110119 11

Pmel17 is a melanocyte/melanoma-specific protein that traffics to melanosomes where it forms a fibrillar matrix on which melanin gets deposited. Before being cleaved into smaller fibrillogenic fragments the protein undergoes processing by proprotein convertases, a class of serine proteases that typically recognize the canonical motif RX(R/K)R↓. The current model of Pmel17 maturation states that this processing step occurs in melanosomes, but in light of recent reports this issue has become contr ...[more]

PMID: 21247888

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Project description:Proprotein convertases (PCs), also known as eukaryotic subtilases, are a group of serine proteases comprising furin (PACE), PC1 (PC3), PC2, PC4, PACE4, PC5 (PC6), and PC7 (LPC, PC8) that generate bioactive proteins and peptides, such as hormones, receptors, and growth factors by cleaving precursor proteins at multibasic motifs. Two other family members, SKI-1/S1P and PCSK9, cleave regulator proteins involved in cholesterol and fatty acid homeostasis at nonbasic peptide bonds. Furin is ubiquitous in eukaryotic tissues and cells. PACE4, PC5, and PC7 are also widespread, whereas the expression of the other PCs is more restricted. PCs are synthesized as multi-segmented zymogens which are autocatalytically activated. The prodomains have regulatory and inhibitory functions. The catalytic domains are the most conserved domains among the PCs. The architecture of the catalytic active furin domain is known in different binding states. The C-terminal parts of the PCs differ in length and structure and contain encoded peptide signatures guiding the PCs to the subcellular destinations on the secretory pathways: SKI-1/S1P to the cis-Golgi, furin, PC5B, and PC7 to the TGN region but also to the plasma membrane. PACE4, PC5A, and PCSK9 are attached at the cell surface. Truncated, soluble furin and SKI-1/S1P, as well as PC1 and PC2, are released into the extracellular matrix. Many enveloped viruses are activated by furin and furin-like PCs and arenaviruses and a few bunyaviruses by SKI-1/S1P. The PCs cleave the viral fusion glycoprotein to trigger fusion of viral envelopes with cellular membranes to deliver the viral genome into host cells. Cleavage by PCs, occasionally in concert with other endoproteases, enables conformational changes in the viral membrane proteins needed for correct oligomerization of glycoprotein spikes and their effective incorporation into virions. Mutational alterations of PC cleavage sites can reduce the fusion potential of viral surface proteins and thus facilitate the development of secure live attenuated vaccines. Alternatively, agents preventing cleavage of viral surface (glyco)proteins block fusion capacity and multicyclic virus replications. PC inhibitors are suggested as promising antiviral drugs for quite a number of viruses causing severe infections.

Dataset Information

Proprotein convertases process Pmel17 during secretion.

Publications

Proprotein convertases process Pmel17 during secretion.

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