The chemorepulsive activity of secreted semaphorins is regulated by furin-dependent proteolytic processing

Abstract

The semaphorins are a large group of cell surface and secreted proteins implicated in axonal pathfinding. Here we show that the secreted mouse semaphorin D (SemD) is synthesized as an inactive precursor (proSemD) and becomes repulsive for sensory and sympathetic neurites upon proteolytic cleavage. ProSemD processing can be blocked completely by an inhibitor selective for furin-like endoproteases or mutagenesis of three conserved dibasic cleavage sites. Its C-terminal pro-peptide contains a processing signal that is essential for SemD to acquire its full repulsive activity. SemD processing is regulated during the embryonic development of the mouse and determines the magnitude of its repulsive activity. Similarly to SemD, the secreted semaphorins SemA and SemE display repulsive properties that are regulated by processing. Our data suggest that differential proteolytic processing determines the repulsive potency of secreted semaphorins and implicate proteolysis as an important regulatory mechanism in axonal pathfinding.

The axonal chemorepellant semaphorin 3A is increased in the cerebellum in schizophrenia and may contribute to its synaptic pathology

“…The heterogeneity is because a combination of proteolytic processing of pro-sema3A and dimerization of sema3A cleavage products. 35,36 Our Western blots of unfractionated protein showed a band of 50 kDa in fetal whole brain (Figure 1b) and 40 kDa in adult cerebellum (Figure 1a), consistent with results seen using a similar carboxy-terminal antibody in HEK293 cells and mouse embryo, respectively. 35,36 The fact that we did not see any clear bands at 125, 95, or 65 kDa, as also reported in some circumstances by these authors, may reflect intrinsically low levels of these sema3A species in human cerebellum, or their susceptibility to perimortem degradation.…”

“…35,36 Our Western blots of unfractionated protein showed a band of 50 kDa in fetal whole brain (Figure 1b) and 40 kDa in adult cerebellum (Figure 1a), consistent with results seen using a similar carboxy-terminal antibody in HEK293 cells and mouse embryo, respectively. 35,36 The fact that we did not see any clear bands at 125, 95, or 65 kDa, as also reported in some circumstances by these authors, may reflect intrinsically low levels of these sema3A species in human cerebellum, or their susceptibility to perimortem degradation. The change in molecular weight between infants and adults may represent a maturational shift in sema3A processing, and be related to the corresponding alteration in sema3A immunoreactivity from being primarily in Purkinje cell bodies (Figure 2b) to the adjacent neuropil (Figure 2a).…”

“…ISH was carried out with a 36-base oligonucleotide probe, complementary to bases 1421-1457 of human reelin mRNA (accession number XM 004972), using methods described previously. 24,33 Briefly, the probe was 3 0 -labelled with[a- 35 S]dATP (B1200 Ci/mmol, PerkinElmer Life Sciences, Hounslow, UK) at a 1:10 ratio using terminal deoxynucleotide transferase and labelling buffer (Promega, Southampton, UK) and purified using Sephadex G-50 columns (Amersham Pharmacia Biotech). Sections were incubated overnight at 311C in hybridization buffer containing 1 Â 10 6 counts per minute of purified labelled probe, and 50 mM dithiothreitol.…”

Measles virus modulates dendritic cell/T‐cell communication at the level of plexinA1/neuropilin‐1 recruitment and activity

“…4B). In addition and in line with previous observations [38,39], a lower molecularweight species was also detected, the activity of which is unknown as yet. For unknown reasons, the mock preparation also caused some SEMA3A production from DC in these cocultures, which was not detected in DC cultures ( Fig.…”

Matrix-Dependent Local Retention of Secretory Vesicle Cargo in Cortical Neurons

“…Variations in the degree of cargo protein processing could affect release characteristics. Proteolytic processing of Sema3A generates a fragment that lacks the basic domain (Adams et al, 1997), which would favor transient events. It is also conceivable that intracellular second messengers influence the release mode: elevated calcium concentrations shift the preferred fusion mode in chromaffin cells (Alés et al, 1999), and cAMP levels influence cargo solubilization and thereby release characteristics in lactotrophs (Angleson et al, 1999).…”