Alteration of endosomal trafficking is associated with early-onset parkinsonism caused by SYNJ1 mutations

Recently, a new form of autosomal recessive early-onset parkinsonism (PARK20), due to mutations in the gene encoding the phosphoinositide phosphatase, Synaptojanin 1 (Synj1), has been reported. Several genes responsible for hereditary forms of Parkinson's disease are implicated in distinct steps of the endolysosomal pathway. However, the nature and the degree of endocytic membrane trafficking impairment in early-onset parkinsonism remains elusive. Here, we show that depletion of Synj1 causes drastic alterations of early endosomes, which become enlarged and more numerous, while it does not affect the morphology of late endosomes both in non-neuronal and neuronal cells. Moreover, Synj1 loss impairs the recycling of transferrin, while it does not alter the trafficking of the epidermal growth factor receptor. The ectopic expression of Synj1 restores the functions of early endosomes, and rescues these trafficking defects in depleted cells. Importantly, the same alterations of early endosomal compartments and trafficking defects occur in fibroblasts of PARK20 patients. Our data indicate that Synj1 plays a crucial role in regulating the homeostasis and functions of early endosomal compartments in different cell types, and highlight defective cellular pathways in PARK20. In addition, they strengthen the link between endosomal trafficking and Parkinson's disease

Targeting the endoplasmic reticulum unfolded protein response to counteract the oxidative stress-Induced endothelial dysfunction

In endothelial cells, the tight control of the redox environment is essential for the maintenance of vascular homeostasis. The imbalance between ROS production and antioxidant response can induce endothelial dysfunction, the initial event of many cardiovascular diseases. Recent studies have revealed that the endoplasmic reticulum could be a new player in the promotion of the pro- or antioxidative pathways and that in such a modulation, the unfolded protein response (UPR) pathways play an essential role. The UPR consists of a set of conserved signalling pathways evolved to restore the proteostasis during protein misfolding within the endoplasmic reticulum. Although the first outcome of the UPR pathways is the promotion of an adaptive response, the persistent activation of UPR leads to increased oxidative stress and cell death. This molecular switch has been correlated to the onset or to the exacerbation of the endothelial dysfunction in cardiovascular diseases. In this review, we highlight the multiple chances of the UPR to induce or ameliorate oxidative disturbances and propose the UPR pathways as a new therapeutic target for the clinical management of endothelial dysfunction

Assembly of the CD8α/p56lck protein complex in stably expressing rat epithelial cells

AbstractWe have previously characterized the biogenesis of the human CD8α protein expressed in rat epithelial cells. We now describe the biosynthesis, post-translational maturation and hetero-oligomeric assembly of the human CD8α/p56lck protein complex in stable transfectants obtained from the same cell line. There were no differences in the myristilation of p56lck, or in the dimerization, O-glycosylation and transport to the plasma membrane of CD8α, between cells expressing either one or both proteins. In the doubly expressing cells, dimeric forms of CD8α established hetero-oligomeric complexes with p56lck, as revealed by co-immunoprecipitation assays performed with anti-CD8α antibody. Moreover, p56lck bound in these hetero-oligomeric complexes was endowed with auto- and hetero-phosphorylating activity. The present study shows that: (1) the newly synthesized p56lck binds rapidly to CD8α and most of the p56lck is bound to CD8α at steady state; (2) CD8α/p56lck protein complexes are formed at internal membranes as well as at the plasma membrane; and (3) about 50% of complexed p56lck reaches the cell surface

Assembly of the CD8alpha/p56(lck) protein complex in stably expressing rat epithelial cells.

AbstractWe have previously characterized the biogenesis of the human CD8α protein expressed in rat epithelial cells. We now describe the biosynthesis, post-translational maturation and hetero-oligomeric assembly of the human CD8α/p56lck protein complex in stable transfectants obtained from the same cell line. There were no differences in the myristilation of p56lck, or in the dimerization, O-glycosylation and transport to the plasma membrane of CD8α, between cells expressing either one or both proteins. In the doubly expressing cells, dimeric forms of CD8α established hetero-oligomeric complexes with p56lck, as revealed by co-immunoprecipitation assays performed with anti-CD8α antibody. Moreover, p56lck bound in these hetero-oligomeric complexes was endowed with auto- and hetero-phosphorylating activity. The present study shows that: (1) the newly synthesized p56lck binds rapidly to CD8α and most of the p56lck is bound to CD8α at steady state; (2) CD8α/p56lck protein complexes are formed at internal membranes as well as at the plasma membrane; and (3) about 50% of complexed p56lck reaches the cell surface