John Fredy Castro-Alvarez

Long- and short-term CDK5 knockdown prevents spatial memory dysfunction and tau pathology of triple transgenic Alzheimer’s mice

CDK5 is a member of the cyclin-dependent kinase family with diverse functions in both the developing and mature nervous system. The inappropriate activation of CDK5 due to the proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles and chronic neurodegeneration. At 18 months of age 3xTg-AD mice were sacrificed after 1 year (long term) or 3 weeks (short term) of CDK5 knockdown. In long-term animals CDK5 knockdown prevented insoluble Tau formation in the hippocampi and prevented spatial memory impairment. In short-term animals, CDK5 knockdown showed reduction of CDK5, reversed Tau aggregation, and improved spatial memory compared to scrambled treated old 3xTg-AD mice. Neither long-term nor short-term CDK5 knock-down had an effect on old littermates. These findings further validate CDK5 as a target for Alzheimer’s disease both as a preventive measure and after the onset of symptoms.

Blastocyst-endometrium interaction: intertwining a cytokine network.

The successful implantation of the blastocyst depends on adequate interactions between the embryo and the uterus. The development of the embryo begins with the fertilized ovum, a single totipotent cell which undergoes mitosis and gives rise to a multicellular structure named blastocyst. At the same time, increasing concentrations of ovarian steroid hormones initiate a complex signaling cascade that stimulates the differentiation of endometrial stromal cells to decidual cells, preparing the uterus to lodge the embryo. Studies in humans and in other mammals have shown that cytokines and growth factors are produced by the pre-implantation embryo and cells of the reproductive tract; however, the interactions between these factors that converge for successful implantation are not well understood. This review focuses on the actions of interleukin-1, leukemia inhibitory factor, epidermal growth factor, heparin-binding epidermal growth factor, and vascular endothelial growth factor, and on the network of their interactions leading to early embryo development, peri-implantatory endometrial changes, embryo implantation and trophoblast differentiation. We also propose therapeutical approaches based on current knowledge on cytokine interactions.

Silencing of CDK5 as potential therapy for Alzheimer ' s disease

Abstract Neurodegeneration is one of the greatest public health challenges for the 21st century. Among neurodegenerative diseases, Alzheimer’s disease (AD) is the most prevalent and best characterized. Nevertheless, despite the large investment in AD research, currently there is no effective therapeutic option. In the present review, we highlight a novel alternative, which takes advantage of the biotechnological outbreak deployed by the discovery of the RNA interference-based gene silencing mechanism, and its application as a tool for neurodegeneration treatment. Here, we highlight cyclin-dependent kinase 5 (CDK5) as a key candidate target for therapeutic gene silencing. Unlike other members of the cyclin-dependent kinase family, CDK5 does not seem to play a crucial role in cell cycle regulation. By contrast, CDK5 participates in multiple functions during nervous system development and has been established as a key mediator of Tau hyperphosphorylation and neurofibrillary pathology, thus serving as an optimal candidate for targeted therapy in the adult nervous system. We propose that the use of RNA interference for CDK5 silencing presents an attractive and specific therapeutic alternative for AD and perhaps against other tauopathies.

Cyclin-Dependent kinase 5 targeting prevents β-Amyloid aggregation involving glycogen synthase kinase 3β and phosphatases

Inappropriate activation of cyclin‐dependent kinase 5 (CDK5) resulting from proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles, β‐amyloid (βA) aggregation, and chronic neurodegeneration. At 18 months of age, 3× Tg‐AD mice were sacrificed after either 3 weeks (short term) or 1 year (long term) of CDK5 knockdown. In short‐term‐treated animals, CDK5 knockdown reversed βA aggregation in the hippocampi via inhibitory phosphorylation of glycogen synthase kinase 3β Ser9 and activation of phosphatase PP2A. In long‐term‐treated animals, CDK5 knockdown induced a persistent reduction in CDK5 and prevented βA aggregation, but the effect on amyloid precursor protein processing was reduced, suggesting that yearly booster therapy would be required. These findings further validate CDK5 as a target for preventing or blocking amyloidosis in older transgenic mice.

Cyclin-dependent kinase 5, a node protein in diminished tauopathy: a systems biology approach

Alzheimers disease (AD) is the most common cause of dementia worldwide. One of the main pathological changes that occurs in AD is the intracellular accumulation of hyperphosphorylated Tau protein in neurons. Cyclin-dependent kinase 5 (CDK5) is one of the major kinases involved in Tau phosphorylation, directly phosphorylating various residues and simultaneously regulating various substrates such as kinases and phosphatases that influence Tau phosphorylation in a synergistic and antagonistic way. It remains unknown how the interaction between CDK5 and its substrates promotes Tau phosphorylation, and systemic approaches are needed that allow an analysis of all the proteins involved. In this review, the role of the CDK5 signaling pathway in Tau hyperphosphorylation is described, an in silico model of the CDK5 signaling pathway is presented. The relationship among these theoretical and computational models shows that the regulation of Tau phosphorylation by PP2A and glycogen synthase kinase 3β (GSK3β) is essential under basal conditions and also describes the leading role of CDK5 under excitotoxic conditions, where silencing of CDK5 can generate changes in these enzymes to reverse a pathological condition that simulates AD.

β-Secretase 1’s Targeting Reduces Hyperphosphorilated Tau, Implying Autophagy Actors in 3xTg-AD Mice

β-site APP cleaving enzyme 1 (BACE1) initiates APP cleavage, which has been reported to be an inducer of tau pathology by altering proteasome functions in Alzheimer’s disease (AD). However, the exact relationship between BACE1 and PHF (Paired Helical Filaments) formation is not clear. In this study, we confirm that BACE1 and Hsc70 are upregulated in the brains of AD patients, and we demonstrate that both proteins show enhanced expression in lipid rafts from AD-affected triple transgenic mouse brains. BACE1 targeting increased Hsc70 levels in the membrane and cytoplasm fractions and downregulated Hsp90 and CHIP in the nucleus in the hippocampi of 3xTg-AD mice. However, these observations occurred in a proteasome-independent manner in vitro. The BACE1miR-induced reduction of soluble hyperphosphorylated tau was associated with a decrease in MAPK activity. However, the BACE1 RNAi-mediated reduction of hyperphosphorylated tau was only blocked by 3-MA (3-methyladenine) in vitro, and it resulted in the increase of Hsc70 and LAMP2 in lipid rafts from hippocampi of 3xTg-AD mice, and upregulation of survival and homeostasis signaling. In summary, our findings suggest that BACE1 silencing neuroprotects reducing soluble hyperphosphorylated tau, modulating certain autophagy-related proteins in aged 3xTg-AD mice.

Specific de-SUMOylation triggered by acquisition of spatial learning is related to epigenetic changes in the rat hippocampus.

Histone acetyltransferase activity by transcriptional cofactors such as CREB-binding protein (CBP) and post-translational modifications by small ubiquitin-like modifier-1 (SUMO-1) have shown to be relevant for synaptic and neuronal activity. Here, we investigate whether SUMOylation of CBP plays a role in spatial learning. We assessed protein levels of CBP/p300, SUMO-1, and CBP SUMOylation in the hippocampi of rats trained on the Morris water maze task. Furthermore, we evaluated the post-translational modifications at Zif268, BDNF, and Arc/Arg3.1 promoters using chromatin immunoprecipitation with anti-Acetyl-Histone H3-Lys14 (H3K14Ac) and SUMO-1. We found that CBP/p300 protein expression is unchanged in animals trained for 7 days. However, H3K14Ac-specific histone acetyltransferase activity showed specific hyperacetylation at promoters of Zif268 and BDNF-pI but not of Arc/Arg3.1 and BDNF-pIV. In naive animals, CBP is selectively SUMOylated and the Arc/Arg3.1 promoter is differentially occupied by SUMO-1, although SUMO-1 levels are unchanged. These results suggest a specific negative regulation by SUMO-1 on CBP function and its effect on epigenetic changes triggered by spatial learning and memory processes.

Cyclin-Dependent kinase 5 targeting prevents β-Amyloid aggregation involving glycogen synthase kinase 3β and phosphatases: CDK5 RNAi Prevents β-Amyloidosis

Inappropriate activation of cyclin‐dependent kinase 5 (CDK5) resulting from proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles, β‐amyloid (βA) aggregation, and chronic neurodegeneration. At 18 months of age, 3× Tg‐AD mice were sacrificed after either 3 weeks (short term) or 1 year (long term) of CDK5 knockdown. In short‐term‐treated animals, CDK5 knockdown reversed βA aggregation in the hippocampi via inhibitory phosphorylation of glycogen synthase kinase 3β Ser9 and activation of phosphatase PP2A. In long‐term‐treated animals, CDK5 knockdown induced a persistent reduction in CDK5 and prevented βA aggregation, but the effect on amyloid precursor protein processing was reduced, suggesting that yearly booster therapy would be required. These findings further validate CDK5 as a target for preventing or blocking amyloidosis in older transgenic mice.

CDK5 targeting prevents β-amyloid aggregation involving GSK3 β and phosphatases

Inappropriate activation of cyclin‐dependent kinase 5 (CDK5) resulting from proteolytic release of the activator fragment p25 from the membrane contributes to the formation of neurofibrillary tangles, β‐amyloid (βA) aggregation, and chronic neurodegeneration. At 18 months of age, 3× Tg‐AD mice were sacrificed after either 3 weeks (short term) or 1 year (long term) of CDK5 knockdown. In short‐term‐treated animals, CDK5 knockdown reversed βA aggregation in the hippocampi via inhibitory phosphorylation of glycogen synthase kinase 3β Ser9 and activation of phosphatase PP2A. In long‐term‐treated animals, CDK5 knockdown induced a persistent reduction in CDK5 and prevented βA aggregation, but the effect on amyloid precursor protein processing was reduced, suggesting that yearly booster therapy would be required. These findings further validate CDK5 as a target for preventing or blocking amyloidosis in older transgenic mice.