Many cell types contain subpopulations of microtubules that resist depolymerizing conditions, such as exposure to cold or to the drug nocodazole. This stabilization is due mainly to polymer association with STOP proteins. In mouse, neurons express two major variants of these proteins, N-STOP and E-STOP (120 kDa and 79 kDa, respectively), whereas fibroblasts express F-STOP (42 kDa) and two minor variants of 48 and 89 kDa. N- and E-STOP induce microtubule resistance to both cold and nocodazole exposure, whereas F-STOP confers microtubule stability only to the cold. Here, we investigated the expression of STOP proteins in oligodendrocytes and astrocytes in culture. We found that STOP proteins were expressed in precursor cells, in immature and mature oligodendrocytes, and in astrocytes. We found that oligodendrocytes express a major STOP variant of 89 kDa, which we called O-STOP, and two minor variants of 42 and 48 kDa. The STOP variants expressed by oligodendrocytes induce microtubule resistance to the cold and to nocodazole. For astrocytes, we found the expression of two STOP variants of 42 and 48 kDa and a new STOP isoform of 60 kDa, which we called A-STOP. The STOP variants expressed by astrocytes induce microtubule resistance to the cold but not to nocodazole, as fibroblast variants. In conclusion, astrocytes and oligodendrocytes express different isoforms of STOP protein, which show different microtubule-stabilizing capacities.
"STOP protein levels were detected by western blot analysis: total brains or micro-dissected regions from WT, KO, and Het STOP mice were homogenized in radioimmunoprecipitation assay Buffer (50 Mm Tris pH 8, 150mM NaCl, 1% NP40, 0.5% sodium desoxycholate and 0.1% sodium dodecyl sulfate) and centrifuged at 21 000g for 20min at 4°C. Supernatants (5 µg) were resolved on SDS-PAGE and revealed using primary [MAP6, 23C antibody24 and Neurone Specific Enolase (Millipore)] and secondary antibodies coupled to horseradish peroxidase. "
[Show abstract][Hide abstract] ABSTRACT: Background:
STOP/MAP6 null (KO) mice recapitulate behavioral abnormalities related to positive and negative symptoms and cognitive deficits of schizophrenia. Here, we investigated whether decreased expression of STOP/MAP6 proteins in heterozygous mice (only one allele expressed) would result in abnormal behavior related to those displayed by STOP null mice.
Using a comprehensive test battery, we investigated the behavioral phenotype of STOP heterozygous (Het) mice compared with STOP KO and wild type (WT) mice on animals raised either in standard conditions (controls) or submitted to maternal deprivation.
Control Het mice displayed prominent deficits in social interaction and learning, resembling KO mice. In contrast, they exhibited short-lasting locomotor hyperreactivity to acute mild stress and no impaired locomotor response to amphetamine, much like WT mice. Additionally, perinatal stress deteriorated Het mouse phenotype by exacerbating alterations related to positive symptoms such as their locomotor reactivity to acute mild stress and psychostimulant challenge.
Results show that the dosage of susceptibility genes modulates their putative phenotypic contribution and that STOP expression has a high penetrance on cognitive abilities. Hence, STOP Het mice might be useful to investigate cognitive defects related to those observed in mental diseases and ultimately might be a valuable experimental model to evaluate preventive treatments.
"No signal was observed either in the GST-Bmcc1s/lysis buffer or in GST/brain lysate eluates, indicating the specificity of the Bmcc1s-MAP6 interaction (Fig. 6B). Several MAP6 isoforms were revealed in the GST-Bmcc1s/brain lysate eluate, namely the neuronal isoforms N-STOP (120 kDa) and E-STOP (80 kDa), the astrocyte isoform A-STOP (60 KDa) and a fibroblastic and astroglial 48 kDa isoform , . In contrast, the main MAP6 fibroblast isoform F-STOP (42 kDa), also weakly expressed in astrocytes and neurons, was not detected. "
[Show abstract][Hide abstract] ABSTRACT: The BCH (BNIP2 and Cdc42GAP Homology) domain-containing protein Bmcc1/Prune2 is highly enriched in the brain and is involved in the regulation of cytoskeleton dynamics and cell survival. However, the molecular mechanisms accounting for these functions are poorly defined. Here, we have identified Bmcc1s, a novel isoform of Bmcc1 predominantly expressed in the mouse brain. In primary cultures of astrocytes and neurons, Bmcc1s localized on intermediate filaments and microtubules and interacted directly with MAP6/STOP, a microtubule-binding protein responsible for microtubule cold stability. Bmcc1s overexpression inhibited MAP6-induced microtubule cold stability by displacing MAP6 away from microtubules. It also resulted in the formation of membrane protrusions for which MAP6 was a necessary cofactor of Bmcc1s. This study identifies Bmcc1s as a new MAP6 interacting protein able to modulate MAP6-induced microtubule cold stability. Moreover, it illustrates a novel mechanism by which Bmcc1 regulates cell morphology.
PLoS ONE 04/2012; 7(4):e35488. DOI:10.1371/journal.pone.0035488 · 3.23 Impact Factor
"Animals Stable tubule only polypeptide deficient mice were obtained by putting the lacZ gene in the place of the exon 1 of STOP gene (MAP6, Denarier et al. 1998), present in all characterized STOP isoforms (A-, E-, F-, N-and O-STOP, Aguezzoul et al. 2003; Galiano et al. 2004). Thus, the exon 1 deletion results in the absence of any detectable STOP isoforms in STOP KO mice (Andrieux et al. 2002). "
[Show abstract][Hide abstract] ABSTRACT: The deletion of microtubule-associated protein stable tubule only polypeptide (STOP) leads to neuroanatomical, biochemical and severe behavioral alterations in mice, partly alleviated by antipsychotics. Therefore, STOP knockout (KO) mice have been proposed as a model of some schizophrenia-like symptoms. Preliminary data showed decreased brain serotonin (5-HT) tissue levels in STOP KO mice. As literature data demonstrate various interactions between microtubule-associated proteins and 5-HT, we characterized some features of the serotonergic neurotransmission in STOP KO mice. In the brainstem, mutant mice displayed higher tissue 5-HT levels and in vivo synthesis rate, together with marked increases in 5-HT transporter densities and 5-HT1A autoreceptor levels and electrophysiological sensitivity, without modification of the serotonergic soma number. Conversely, in projection areas, STOP KO mice exhibited lower 5-HT levels and in vivo synthesis rate, associated with severe decreases in 5-HT transporter densities, possibly related to reduced serotonergic terminals. Mutant mice also displayed a deficit of adult hippocampal neurogenesis, probably related to both STOP deletion and 5-HT depletion. Finally, STOP KO mice exhibited a reduced anxiety- and, probably, an increased helpness-status, that could be because of the strong imbalance of the serotonin neurotransmission between somas and terminals. Altogether, these data suggested that STOP deletion elicited peculiar 5-HT disconnectivity.
Journal of Neurochemistry 10/2010; 115(6):1579-94. DOI:10.1111/j.1471-4159.2010.07064.x · 4.28 Impact Factor
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