Interaction of PLP with GFP-MAL2 in the Human Oligodendroglial Cell Line HOG

The velocity of the nerve impulse conduction of vertebrates relies on the myelin sheath, an electrically insulating layer that surrounds axons in both the central and peripheral nervous systems, enabling saltatory conduction of the action potential. Oligodendrocytes are the myelin-producing glial cells in the central nervous system. A deeper understanding of the molecular basis of myelination and, specifically, of the transport of myelin proteins, will contribute to the search of the aetiology of many dysmyelinating and demyelinating diseases, including multiple sclerosis. Recent investigations suggest that proteolipid protein (PLP), the major myelin protein, could reach myelin sheath by an indirect transport pathway, that is, a transcytotic route via the plasma membrane of the cell body. If PLP transport relies on a transcytotic process, it is reasonable to consider that this myelin protein could be associated with MAL2, a raft protein essential for transcytosis. In this study, carried out with the human oligodendrocytic cell line HOG, we show that PLP colocalized with green fluorescent protein (GFP)-MAL2 after internalization from the plasma membrane. In addition, both immunoprecipitation and immunofluorescence assays, indicated the existence of an interaction between GFP-MAL2 and PLP. Finally, ultrastructural studies demonstrated colocalization of GFP-MAL2 and PLP in vesicles and tubulovesicular structures. Taken together, these results prove for the first time the interaction of PLP and MAL2 in oligodendrocytic cells, supporting the transcytotic model of PLP transport previously suggested

Brain plasminogen system

Endothelial cells, glial and neuronal cells, representing the principal sources of plasminogen activator (tPA and uPA), are in close interaction in the neurovascular unit. Formation of plasmin at the surface of endothelial cells and neurons has important consequences on these cells (apoptosis of endothelial cells and detachment/aggregation of neurons). The plasminogen activation system is also known to participate in various inflammatory conditions of the central nervous system. In such pathologies, beyond circulating plasminogen, the origin of plasminogen is still a matter of debate. First, we have investigated the presence of plasminogen in human cerebro-spinal fluids. The presence of plasminogen and the activity of plasmin, tPA and uPA in inflammatory diseases (GBS, Guillain Barre Syndrome patients, n = 14; MS, Multiple sclerosis, n = 9) and also in non-inflammatory diseases (n = 13) were studied. Western blotting, zymography and chromogenic detection were used to evaluate antigens and activity of plasmin(ogen), uPA and tPA. In human, plasminogen was detectable in both inflammatory (66%) and non-inflammatory (65%) patients. Plasminogen was found in larger concentration in inflammatory diseases (4.6 nM in GBS, 6.5 nM in MS and 2.2 nM in non inflammatory diseases). Active plasmin was detected in GBS and MS patients (3.55 nM vs. 2.6 nM). uPA was detectable in a minority of patients (15% of GBS, 20% if MS and 7% of non-inflammatory diseases), and tPA was not detect. To further investigate the origin of plasminogen in the central nervous system, we are currently exploring the presence of plasminogen in mouse parenchyma in physiological and inflammatory conditions by immuno-histochemistry. In conclusion, we have shown that a plasminogen activation system is detectable in CSF of patient with inflammatory and non-inflammatory diseases. The role of these proteolytic messengers in diseases outcome remains to be determined

Plasminogen in cerebrospinal fluid originates from circulating blood.

Abstract Background: Plasminogen activation is a ubiquitous source of fibrinolytic and proteolytic activity. Besides its role in prevention of thrombosis, plasminogen is involved in inflammatory reactions in the central nervous system. Plasminogen has been detected in the cerebrospinal fluid (CSF) of patients with inflammatory diseases; however, its origin remains controversial, as the blood–CSF barrier may restrict its diffusion from blood. Methods: We investigated the origin of plasminogen in CSF using Alexa Fluor 488–labelled rat plasminogen injected into rats with systemic inflammation and blood–CSF barrier dysfunction provoked by lipopolysaccharide (LPS). Near-infrared fluorescence imaging and immunohistochemistry fluorescence microscopy were used to identify plasminogen in brain structures, its concentration and functionality were determined by Western blotting and a chromogenic substrate assay, respectively. In parallel, plasminogen was investigated in CSF from patients with Guillain-Barré syndrome (n = 15), multiple sclerosis (n = 19) and noninflammatory neurological diseases (n = 8). Results: Endogenous rat plasminogen was detected in higher amounts in the CSF and urine of LPS-treated animals as compared to controls. In LPS-primed rats, circulating Alexa Fluor 488–labelled rat plasminogen was abundantly localized in the choroid plexus, CSF and urine. Plasminogen in human CSF was higher in Guillain-Barré syndrome (median = 1.28 ng/μl (interquartile range (IQR) = 0.66 to 1.59)) as compared to multiple sclerosis (median = 0.3 ng/μl (IQR = 0.16 to 0.61)) and to noninflammatory neurological diseases (median = 0.27 ng/μl (IQR = 0.18 to 0.35)). Conclusions: Our findings demonstrate that plasminogen is transported from circulating blood into the CSF of rats via the choroid plexus during inflammation. Our data suggest that a similar mechanism may explain the high CSF concentrations of plasminogen detected in patients with inflammation-derived CSF barrier impairment

Cognitive and Brain Profiles Associated with Current Neuroimaging Biomarkers of Preclinical Alzheimer's Disease.

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