Role of Calmodulin in Neurodegeneration and Neuroprotection.

Intracellular calcium (Ca2+) levels are critical in maintaining cellular activities and are tightly regulated. Neuronal degeneration and regeneration rely on calcium-binding proteins. Calmodulin (CaM) is a calcium sensor and the primary regulator of receptors and ion channels that maintain calcium homeostasis.

Leucine-rich repeat kinase 2 regulates Sec16A at ER exit sites to allow ER-Golgi export.

Leucine-rich repeat kinase 2 (LRRK2) has been associated with Parkinson's disease (PD) and other disorders. However, its normal physiological functions and pathogenic properties remain elusive. Here we show that LRRK2 regulates the anterograde ER-Golgi transport through anchoring Sec16A at the endoplasmic reticulum exit sites (ERES).

Regulation of neuronal cytoskeletal protein phosphorylation in neurodegenerative diseases.

Neuronal cytoskeletal proteins such as neurofilaments (NFs) and tau are aberrantly and hyperphosphorylated in neurodegeneration. Under normal physiological conditions, NFs are synthesized in the cell bodies and phosphorylated and transported in the axonal compartment. However, under neurodegenerative disorders such as Alzheimer's disease (AD), spinal cord motor neuron inclusions of amyotrophic lateral sclerosis, Lewy bodies of Parkinson's disease, Pick's disease, Charcot-Marie-Tooth disease, and diabetic neuropathy, NFs are aberrantly and hyperphosphorylated in cell bodies.

Regulation of Sox6 by cyclin dependent kinase 5 in brain.

Cyclin dependent kinase 5 (Cdk5) is a proline-directed Ser/Thr kinase involved in various biological functions during normal brain development and neurodegeneration. In brain, Cdk5 activity is specific to post-mitotic neurons, due to neuronal specific expression of its activator p35. The biological functions of Cdk5 have been ascribed to its cytoplasmic substrates, however not much is known in nucleus.

Achaete-scute homologue-1 (ASH1) stimulates migration of lung cancer cells through Cdk5/p35 pathway.

Our previous data suggested that the human basic helix-loop-helix transcription factor achaete-scute homologue-1 (hASH1) may stimulate both proliferation and migration in the lung. In the CNS, cyclin-dependent kinase 5 (Cdk5) and its activator p35 are important for neuronal migration that is regulated by basic helix-loop-helix transcription factors. Cdk5/p35 may also play a role in carcinogenesis.

Cyclin-dependent kinase 5 regulates E2F transcription factor through phosphorylation of Rb protein in neurons.

Recent studies have shown the involvement of cyclin-dependent kinase 5 (Cdk5) in cell cycle regulation in postmitotic neurons. In this study, we demonstrate that Cdk5 and its co-activator p35 were detected in the nuclear fraction in neurons and Cdk5/p35 phosphorylated retinoblastoma (Rb) protein, a key protein controlling cell cycle re-entry. Cdk5/p35 phosphorylates Rb at the sites similar to those phosphorylated by Cdk4 and Cdk2.

Direct evidence of phosphorylated neuronal intermediate filament proteins in neurofibrillary tangles (NFTs): phosphoproteomics of Alzheimer's NFTs.

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by brain pathology of intracellular neurofibrillary tangles (NFTs) and extracellular amyloid plaques. NFTs contain aberrantly hyperphosphorylated Tau as paired helical filaments (PHFs). Although NFs have been shown immunohistologically to be part of NFTs, there has been debate that the identity of NF proteins in NFTs is due to the cross-reactivity of phosphorylated NF antibodies with phospho-Tau.

Phosphorylation of p27Kip1 at Thr187 by cyclin-dependent kinase 5 modulates neural stem cell differentiation.

Cyclin-dependent kinase 5 (Cdk5) plays a key role in the development of the mammalian nervous system; it phosphorylates a number of targeted proteins involved in neuronal migration during development to synaptic activity in the mature nervous system. Its role in the initial stages of neuronal commitment and differentiation of neural stem cells (NSCs), however, is poorly understood. In this study, we show that Cdk5 phosphorylation of p27(Kip1) at Thr187 is crucial to neural differentiation because 1) neurogenesis is specifically suppressed by transfection of p27(Kip1) siRNA into Cdk5(+/+) NSCs; 2) reduced neuronal differentiation in Cdk5(-/-) compared with Cdk5(+/+) NSCs; 3) Cdk5(+/+) NSCs, whose differentiation is inhibited by a nonphosphorylatable mutant, p27/Thr187A, are rescued by cotransfection of a phosphorylation-mimicking mutant, p27/Thr187D; and 4) transfection of mutant p27(Kip1) (p27/187A) into Cdk5(+/+) NSCs inhibits differentiation.

A 24-residue peptide (p5), derived from p35, the Cdk5 neuronal activator, specifically inhibits Cdk5-p25 hyperactivity and tau hyperphosphorylation.

The activity of Cdk5-p35 is tightly regulated in the developing and mature nervous system. Stress-induced cleavage of the activator p35 to p25 and a p10 N-terminal domain induces deregulated Cdk5 hyperactivity and perikaryal aggregations of hyperphosphorylated Tau and neurofilaments, pathogenic hallmarks in neurodegenerative diseases, such as Alzheimer disease and amyotrophic lateral sclerosis, respectively. Previously, we identified a 125-residue truncated fragment of p35 called CIP that effectively and specifically inhibited Cdk5-p25 activity and Tau hyperphosphorylation induced by Aβ peptides in vitro, in HEK293 cells, and in neuronal cells.

Quantitative phosphoproteomic analysis of neuronal intermediate filament proteins (NF-M/H) in Alzheimer's disease by iTRAQ.

Aberrant hyperphosphorylation of neuronal cytoskeletal proteins is one of the major pathological hallmarks of neurodegenerative disorders such as Alzheimer disease (AD), amyotrophic lateral sclerosis (ALS), and Parkinson's disease (PD). Human NF-M/H display a large number of multiple KSP repeats in the carboxy-terminal tail domain, which are phosphorylation sites of proline-directed serine/threonine (pSer/Thr-Pro, KS/T-P) kinases. The phosphorylation sites of NF-M/H have not been characterized in AD brain.

Phosphorylation-specific peptidyl-prolyl isomerization of neuronal cytoskeletal proteins by Pin1: implications for therapeutics in neurodegeneration.

Pin1 [Protein Interacting with NIMA (never in mitosis A)] is a peptidyl prolyl cis-trans isomerase that isomerizes phospho-Serine/Threonine-Proline [p(S/T)-P] motifs of its target proteins. Pin1 functions in concert with proline directed kinases such as cyclin-dependent protein kinases, extracellular signal-regulated kinases, and c-Jun N- terminal kinase, and protein phosphatases such as protein phosphatase 2A (PP2A) and PP2B, in the regulation of a wide range of cellular processes including cell division, DNA damage response, and gene transcription, and in susceptibility to cancer and neurodegenerative diseases. This review focuses on the roles of Pin1 in neurodegenerative disorders including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Frontotemporal dementia associated with parkinsonism linked to chromosome 17.

Peptidyl-prolyl isomerase 1 regulates protein phosphatase 2A-mediated topographic phosphorylation of neurofilament proteins.

In normal neurons, neurofilament (NF) proteins are phosphorylated in the axonal compartment. However, in neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS), NF proteins are aberrantly hyperphosphorylated within the cell bodies. The aberrant hyperphosphorylation of NF accumulations found in neurodegeneration could be attributable to either deregulation of proline-directed Ser/Thr kinase(s) activity or downregulation of protein phosphatase(s) activity.

Tumor necrosis factor-alpha regulates cyclin-dependent kinase 5 activity during pain signaling through transcriptional activation of p35.

Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase. We have previously reported that Cdk5 participates in the regulation of nociceptive signaling, and the expression of Cdk5 and its activator, p35, are up-regulated in nociceptive neurons during peripheral inflammation. The aim of our current study was to identify the proinflammatory molecules that regulate Cdk5/p35 activity in response to inflammation.

Pin1-dependent prolyl isomerization modulates the stress-induced phosphorylation of high molecular weight neurofilament protein.

Aberrant phosphorylation of neuronal cytoskeletal proteins is a key pathological event in neurodegenerative disorders such as Alzheimer disease (AD) and amyotrophic lateral sclerosis, but the underlying mechanisms are still unclear. Previous studies have shown that Pin1, a peptidylprolyl cis/trans-isomerase, may be actively involved in the regulation of Tau hyperphosphorylation in AD. Here, we show that Pin1 modulates oxidative stress-induced NF-H phosphorylation.

Cyclin-dependent kinase 5 phosphorylation of human septin SEPT5 (hCDCrel-1) modulates exocytosis.

Cyclin-dependent kinase 5 (Cdk5) is predominantly expressed in the nervous system, where it is involved in neuronal migration, synaptic transmission, and survival. The role of Cdk5 in synaptic transmission is mediated by regulating the cellular functions of presynaptic proteins such as synapsin, Munc18, and dynamin 1. Its multifunctional role at the synapse is complex and probably involves other novel substrates.

Genome-wide analysis and experimentation of plant serine/ threonine/tyrosine-specific protein kinases.

Protein tyrosine phosphorylation plays an important role in cell growth, development and oncogenesis. No classical protein tyrosine kinase has hitherto been cloned from plants. Does protein tyrosine kinase exist in plants? To address this, we have performed a genomic survey of protein tyrosine kinase motifs in plants using the delineated tyrosine phosphorylation motifs from the animal system.

Functional characterization of peanut serine/threonine/tyrosine protein kinase: molecular docking and inhibition kinetics with tyrosine kinase inhibitors.

Serine/threonine/tyrosine (STY) protein kinase from peanut is developmentally regulated and is induced by abiotic stresses. In addition, STY protein kinase activity is regulated by tyrosine phosphorylation. Kinetic mechanism of plant dual specificity protein kinases is not studied so far.

Mutational analysis of stress-responsive peanut dual specificity protein kinase. Identification of tyrosine residues involved in regulation of protein kinase activity.

We recently reported that Arachis hypogaea serine/threonine/tyrosine (STY) protein kinase is developmentally regulated and is induced by abiotic stresses (Rudrabhatla, P., and Rajasekharan, R. (2002) Plant Physiol.

Developmentally regulated dual-specificity kinase from peanut that is induced by abiotic stresses.

Tyrosine (Tyr) phosphorylation represents an important biochemical mechanism to regulate many cellular processes. No Tyr kinase has been cloned so far in plants. Dual-specificity kinases are reported in plants and the function of these kinases remains unknown.