Brain-Derived Neurotrophic Factor influences cholesterol trafficking between astrocytes and neurons - Effects of Aging or a Fructose-rich diet on neurotrophin levels and markers of brain functioning

Cholesterol is critical to maintain membrane plasticity, cellular function and synaptic integrity. The neurotrophin Brain-derived neurotrophic factor (BDNF) exerts a critical role in brain synaptic plasticity, learning and memory. It was previously reported that BDNF elicits cholesterol biosynthesis and promote the accumulation of presynaptic proteins in cholesterol-rich lipid rafts, but no further data are available on its ability to modulate physiological mechanisms involved in brain cholesterol homeostasis. One aim of this PhD research project was to investigate whether BDNF influences cholesterol homeostasis, focusing on the effect of the neurotrophin on Apolipoprotein E (ApoE) synthesis, cholesterol efflux from astrocytes and cholesterol incorporation into neurons. Our results show that BDNF significantly stimulates cholesterol efflux by astrocytes, as well as ATP binding cassette A1 (ABCA1) transporter and the expression of ApoE in cellular models of human astrocytes. On the other hand, BDNF reduce cholesterol incorporation in neurons by enhancing LXR-beta expression, protecting these cells from cholesterol excess-induced apoptosis. These results evidence a novel role of BDNF in the modulation of ApoE and cholesterol homeostasis in glial and neuronal cells. A further objective of this research project was to investigate the effects of a short-term (two-weeks) fructose-rich diet on brain redox homeostasis, autophagy, as well as on BDNF, its receptor TrkB and synaptic function markers, in the cortex of young and adults rats, in order to highlight the early risks to which brain is exposed. The results showed that a short-term fructose feeding was associated with an imbalance of redox homeostasis, as lower amount of Nuclear factor (erythroid derived 2)-like 2, lower activity of Glucose 6-phosphate dehydrogenase and Glutathione reductase, together with lower GSH/GSSG ratio, were found in fructose-fed young and adult rats. Fructose-rich diet was also associated with the activation of autophagy, as higher levels of Beclin, LC3 II and P62 were detected in cortex of fructose-fed rats. A diet-associated decrease of synaptophysin, synapsin I, and synaptotagmin I, suggests an impairment of synaptic transmission in fructose-fed young and adult rats. Interestingly, BDNF amount was significantly lower only in fructose-fed adult rats, while the level of its receptor TrkB decreased in both group of treated rats. A further marker of brain functioning, Acetylcholinesterase activity was found increased only in fructose-fed young animals. Overall, our findings suggest that young rats may severely suffer from the deleterious influence of fructose on brain health as the adults and provide experimental data suggesting the need of targeted nutritional strategies to reduce its amount in foods

PAK6-mediated phosphorylation of PPP2R2C regulates LRRK2-PP2A complex formation

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of inherited and sporadic Parkinson’s disease (PD) and previous work suggests that dephosphorylation of LRRK2 at a cluster of heterologous phosphosites is associated to disease. We have previously reported subunits of the PP1 and PP2A classes of phosphatases as well as the PAK6 kinase as regulators of LRRK2 dephosphorylation. We therefore hypothesized that PAK6 may have a functional link with LRRK2’s phosphatases. To investigate this, we used PhosTag gel electrophoresis with purified proteins and found that PAK6 phosphorylates the PP2A regulatory subunit PPP2R2C at position S381. While S381 phosphorylation did not affect PP2A holoenzyme formation, a S381A phosphodead PPP2R2C showed impaired binding to LRRK2. Also, PAK6 kinase activity changed PPP2R2C subcellular localization in a S381 phosphorylation-dependent manner. Finally, PAK6-mediated dephosphorylation of LRRK2 was unaffected by phosphorylation of PPP2R2C at S381, suggesting that the previously reported mechanism whereby PAK6-mediated phosphorylation of 14-3-3 proteins promotes 14-3-3-LRRK2 complex dissociation and consequent exposure of LRRK2 phosphosites for dephosphorylation is dominant. Taken together, we conclude that PAK6-mediated phosphorylation of PPP2R2C influences the recruitment of PPP2R2C to the LRRK2 complex and PPP2R2C subcellular localization, pointing to an additional mechanism in the fine-tuning of LRRK2 phosphorylation

PAK6-mediated phosphorylation of PPP2R2C regulates LRRK2-PP2A complex formation

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of inherited and sporadic Parkinson's disease (PD) and previous work suggests that dephosphorylation of LRRK2 at a cluster of heterologous phosphosites is associated to disease. We have previously reported subunits of the PP1 and PP2A classes of phosphatases as well as the PAK6 kinase as regulators of LRRK2 dephosphorylation. We therefore hypothesized that PAK6 may have a functional link with LRRK2's phosphatases. To investigate this, we used PhosTag gel electrophoresis with purified proteins and found that PAK6 phosphorylates the PP2A regulatory subunit PPP2R2C at position S381. While S381 phosphorylation did not affect PP2A holoenzyme formation, a S381A phosphodead PPP2R2C showed impaired binding to LRRK2. Also, PAK6 kinase activity changed PPP2R2C subcellular localization in a S381 phosphorylation-dependent manner. Finally, PAK6-mediated dephosphorylation of LRRK2 was unaffected by phosphorylation of PPP2R2C at S381, suggesting that the previously reported mechanism whereby PAK6-mediated phosphorylation of 14-3-3 proteins promotes 14-3-3-LRRK2 complex dissociation and consequent exposure of LRRK2 phosphosites for dephosphorylation is dominant. Taken together, we conclude that PAK6-mediated phosphorylation of PPP2R2C influences the recruitment of PPP2R2C to the LRRK2 complex and PPP2R2C subcellular localization, pointing to an additional mechanism in the fine-tuning of LRRK2 phosphorylation.</p

The Roc domain of LRRK2 as a hub for protein-protein interactions:a focus on PAK6 and its impact on RAB phosphorylation

Leucine-rich repeat kinase 2 (LRRK2) has taken center stage in Parkinson's disease (PD) research as mutations cause familial PD and more common variants increase lifetime risk for disease. One unique feature in LRRK2 is the coexistence of GTPase/Roc (Ras of complex) and kinase catalytic functions, bridged by a COR (C-terminal Of Roc) platform for dimerization. Multiple PD mutations are located within the Roc/GTPase domain and concomitantly lead to defective GTPase activity and augmented kinase activity in cells, supporting a crosstalk between GTPase and kinase domains. In addition, biochemical and structural data highlight the importance of Roc as a molecular switch modulating LRRK2 monomer-to-dimer equilibrium and building the interface for interaction with binding partners. Here we review the effects of PD Roc mutations on LRRK2 function and discuss the importance of Roc as a hub for multiple molecular interactions relevant for the regulation of cytoskeletal dynamics and intracellular trafficking pathways. Among the well-characterized Roc interactors, we focused on the cytoskeletal-related kinase p21-activated kinase 6 (PAK6). We report the affinity between LRRK2-Roc and PAK6 measured by microscale thermophoresis (MST). We further show that PAK6 can modulate LRRK2-mediated phosphorylation of RAB substrates in the presence of LRRK2 wild-type (WT) or the PD G2019S kinase mutant but not when the PD Roc mutation R1441G is expressed. These findings support a mechanism whereby mutations in Roc might affect LRRK2 activity through impaired protein-protein interaction in the cell

PAK6-mediated phosphorylation of PPP2R2C regulates LRRK2-PP2A complex formation

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of inherited and sporadic Parkinson's disease (PD) and previous work suggests that dephosphorylation of LRRK2 at a cluster of heterologous phosphosites is associated to disease. We have previously reported subunits of the PP1 and PP2A classes of phosphatases as well as the PAK6 kinase as regulators of LRRK2 dephosphorylation. We therefore hypothesized that PAK6 may have a functional link with LRRK2's phosphatases. To investigate this, we used PhosTag gel electrophoresis with purified proteins and found that PAK6 phosphorylates the PP2A regulatory subunit PPP2R2C at position S381. While S381 phosphorylation did not affect PP2A holoenzyme formation, a S381A phosphodead PPP2R2C showed impaired binding to LRRK2. Also, PAK6 kinase activity changed PPP2R2C subcellular localization in a S381 phosphorylation-dependent manner. Finally, PAK6-mediated dephosphorylation of LRRK2 was unaffected by phosphorylation of PPP2R2C at S381, suggesting that the previously reported mechanism whereby PAK6-mediated phosphorylation of 14-3-3 proteins promotes 14-3-3-LRRK2 complex dissociation and consequent exposure of LRRK2 phosphosites for dephosphorylation is dominant. Taken together, we conclude that PAK6-mediated phosphorylation of PPP2R2C influences the recruitment of PPP2R2C to the LRRK2 complex and PPP2R2C subcellular localization, pointing to an additional mechanism in the fine-tuning of LRRK2 phosphorylation.</p

PAK6-mediated phosphorylation of PPP2R2C regulates LRRK2-PP2A complex formation

Mutations in leucine-rich repeat kinase 2 (LRRK2) are a common cause of inherited and sporadic Parkinson's disease (PD) and previous work suggests that dephosphorylation of LRRK2 at a cluster of heterologous phosphosites is associated to disease. We have previously reported subunits of the PP1 and PP2A classes of phosphatases as well as the PAK6 kinase as regulators of LRRK2 dephosphorylation. We therefore hypothesized that PAK6 may have a functional link with LRRK2's phosphatases. To investigate this, we used PhosTag gel electrophoresis with purified proteins and found that PAK6 phosphorylates the PP2A regulatory subunit PPP2R2C at position S381. While S381 phosphorylation did not affect PP2A holoenzyme formation, a S381A phosphodead PPP2R2C showed impaired binding to LRRK2. Also, PAK6 kinase activity changed PPP2R2C subcellular localization in a S381 phosphorylation-dependent manner. Finally, PAK6-mediated dephosphorylation of LRRK2 was unaffected by phosphorylation of PPP2R2C at S381, suggesting that the previously reported mechanism whereby PAK6-mediated phosphorylation of 14-3-3 proteins promotes 14-3-3-LRRK2 complex dissociation and consequent exposure of LRRK2 phosphosites for dephosphorylation is dominant. Taken together, we conclude that PAK6-mediated phosphorylation of PPP2R2C influences the recruitment of PPP2R2C to the LRRK2 complex and PPP2R2C subcellular localization, pointing to an additional mechanism in the fine-tuning of LRRK2 phosphorylation.</p

PUBLIC POLICIES AND CORPORATE WELFARE: THE ITALIAN FIRMS' PROPENSITY TO HIRE WOMEN

Female employment in Italy is still characterized by a strong vertical and horizontal segregation. And yet the relevance of a wider female participation in the labor market is widely recognized in the economic and organizational literature. Unfortunately, the stereotype of the ideal worker does not fit with that of the ideal father or mother. In this way, a work - family conflict arises and favors neither the individual nor the organization. According to these remarks, several stereotypes affect the allocation of family roles and the division of work in companies at the same time. In order to increase female employment, many legislative reforms were made in Italy in the last year. In Italy, the employers’ propensity to hire women is quite low and they are mainly inclined to hire women in part-time jobs. By focusing on the Italian context, our research questions are: why does it happen? Do stereotypes still affect the propensity to hire women in Italy? Are women still fighting between work and family? The purpose of this work is to explore the Italian propensity to hire by gender and compare employees' perspective with that of employers. In order to add knowledge on this phenomenon, we analyzed the most recent data from Excelsior - UNIONCAMERE database. Our finding show some support for the caregiver and housewife stereotype in the Italian context. Moreover, we explore data from European Quality of Life Survey (2012) underlining that from working women perspective there are some evidences for recognize unfounded these stereotypes. The result of this exploration allows us to offer some insights on the research agenda of HR management. We suggest some reflections about the ways of fill gaps in female employment by asking HR managers in creating a more equal-opportunity culture within organizations through corporate policies that may enhance the role of women at work. Obviously, this is a real challenge that requires managers to find some tools for covering the lack of public policies, where it exists, especially at the local level.By focusing on the Italian context, our research questions are: why does it happen? Do stereotypes still affect the propensity to hire women in Italy? Are women still fighting between work and family? The purpose of this work is to explore the Italian propensity to hire by gender and compare employees' perspective with that of employers. In order to add knowledge on this phenomenon, we analyzed the most recent data from Excelsior - UNIONCAMERE database. Our finding show some support for the caregiver and housewife stereotype in the Italian context. Moreover, we explore data from European Quality of Life Survey (2012) underlining that from working women perspective there are some evidences for recognize unfounded these stereotypes. The result of this exploration allows us to offer some insights on the research agenda of HR management. We suggest some reflections about the ways of fill gaps in female employment by asking HR managers in creating a more equal-opportunity culture within or