PAK1 Regulates MEC-17 Acetyltransferase Activity and Microtubule Acetylation during Proplatelet Extension

Alpha-synuclein fine-tunes neuronal response to pro-inflammatory cytokines

Pro-inflammatory cytokines are emerging as neuroinflammatory mediators in Parkinson's disease (PD) due to their ability to act through neuronal cytokine receptors. Critical questions persist regarding the role of cytokines in neuronal dysfunction and their contribution to PD pathology. Specifically, the potential synergy of the hallmark PD protein alpha-synuclein (α-syn) with cytokines is of interest. We therefore investigated the direct impact of pro-inflammatory cytokines on neurons and hypothesized that α-syn pathology exacerbates cytokine-induced neuronal deficits in PD. iPSC-derived cortical neurons (CNs) from healthy controls and patients with α-syn gene locus duplication (SNCA dupl) were stimulated with IL-17A, TNF-α, IFN-γ, or a combination thereof. For rescue experiments, CNs were pre-treated with α-syn anti-oligomerisation compound NPT100-18A prior to IL-17A stimulation. Cytokine receptor expression, microtubule cytoskeleton, axonal transport and neuronal activity were assessed. SNCA dupl CNs displayed an increased IL-17A receptor expression and impaired IL-17A-mediated cytokine receptor regulation. Cytokines exacerbated the altered distribution of tubulin post-translational modifications in SNCA dupl neurites, with SNCA dupl-specific IL-17A effects. Tau pathology in SNCA dupl CNs was also aggravated by IL-17A and cytokine mix. Cytokines slowed down mitochondrial axonal transport, with IL-17A-mediated retrograde slowing in SNCA dupl only. The pre-treatment of SNCA dupl CNs with NPT100-18A prevented the IL-17A-induced functional impairments in axonal transport and neural activity. Our work elucidates the detrimental effects of pro-inflammatory cytokines, particularly IL-17A, on human neuronal structure and function in the context of α-syn pathology, suggesting that cytokine-mediated inflammation represents a second hit to neurons in PD which is amenable to disease modifying therapies that are currently in clinical trials.

The α-tubulin acetyltransferase ATAT1: structure, cellular functions, and its emerging role in human diseases

The acetylation of α-tubulin on lysine 40 is a well-studied post-translational modification which has been associated with the presence of long-lived stable microtubules that are more resistant to mechanical breakdown. The discovery of α-tubulin acetyltransferase 1 (ATAT1), the enzyme responsible for lysine 40 acetylation on α-tubulin in a wide range of species, including protists, nematodes, and mammals, dates to about a decade ago. However, the role of ATAT1 in different cellular activities and molecular pathways has been only recently disclosed. This review comprehensively summarizes the most recent knowledge on ATAT1 structure and substrate binding and analyses the involvement of ATAT1 in a variety of cellular processes such as cell motility, mitosis, cytoskeletal organization, and intracellular trafficking. Finally, the review highlights ATAT1 emerging roles in human diseases and discusses ATAT1 potential enzymatic and non-enzymatic roles and the current efforts in developing ATAT1 inhibitors.

CRISPR genome-wide screening identifies PAK1 as a critical driver of ARSI cross-resistance in prostate cancer progression

Next-generation androgen receptor signaling inhibitors (ARSIs), such as enzalutamide (Enza) and darolutamide (Daro), are initially effective for the treatment of advanced prostate cancer (PCa) and castration-resistant prostate cancer (CRPC). However, patients often relapse and develop cross-resistance, which consequently makes drug resistance an inevitable cause of CRPC-related mortality. By conducting a comprehensive analysis of GEO datasets, CRISPR genome-wide screening results, ATAC-seq data, and RNA-seq data, we systemically identified PAK1 as a significant contributor to ARSI cross-resistance due to the activation of the PAK1/RELA/hnRNPA1/AR-V7 axis. Inhibition of PAK1 followed by suppression of NF-κB pathways and AR-V7 expression effectively overcomes ARSI cross-resistance. Our findings indicate that PAK1 represents a promising therapeutic target gene for the treatment of ARSI cross-resistant PCa patients in the clinic. STATEMENT OF SIGNIFICANCE: PAK1 drives ARSI cross-resistance in prostate cancer progression.

Inhibition of PAK1 generates an ameliorative effect on MPLW515L mouse model of myeloproliferative neoplasms by regulating the differentiation and survival of megakaryocytes

Most thrombopoietin receptor (MPL) mutations result in abnormal megakaryocyte expansion in the spleen or bone marrow (BM), leading to progressive fibrosis. It has been reported that p21 (Rac Family Small GTPase 1 [RAC1])-activated kinase 1 (PAK1) participates in the proliferation and differentiation of megakaryoblasts. PAK1 phosphorylation increased in patients with myeloproliferative neoplasms (MPNs) and murine MPN cells with the Mplw515l mutant gene in this study; however, the function of overactivated PAK1 in MPN cells remains unclear. We found that inhibition of PAK1 caused significant changes in the biological behaviors of MPLW515L mutant cells in vitro, including arrested growth or reduced clonality and increased polyploid DNA and cell apoptosis due to upregulated cleaved caspase 3. In vivo, PAK1 inhibitor treatment caused a slow elevation of leukocytosis and hematocrit (HCT) and a reduction in hepatosplenomegaly in 6133/MPLW515L-transplanted mice, along with reduced tumor cell infiltration and prolonged survival. Further, deletion of PAK1 sustained a relatively normal HCT and platelet count at the beginning of the disease but did not completely alleviate the splenomegaly of MPLW515L mutant mice. Notably, PAK1 knockout attenuated the destruction of splenic structure, and reduced the megakaryocyte burden within the BM. These results suggest that inhibition of PAK1 may be a useful method for treating MPLW515L mutant MPN by intervening megakaryocytes.

Targeting P21-Activated Kinase-1 for Metastatic Prostate Cancer

Metastatic prostate cancer (mPCa) has limited therapeutic options and a high mortality rate. The p21-activated kinase (PAK) family of proteins is important in cell survival, proliferation, and motility in physiology, and pathologies such as infectious, inflammatory, vascular, and neurological diseases as well as cancers. Group-I PAKs (PAK1, PAK2, and PAK3) are involved in the regulation of actin dynamics and thus are integral for cell morphology, adhesion to the extracellular matrix, and cell motility. They also play prominent roles in cell survival and proliferation. These properties make group-I PAKs a potentially important target for cancer therapy. In contrast to normal prostate and prostatic epithelial cells, group-I PAKs are highly expressed in mPCA and PCa tissue. Importantly, the expression of group-I PAKs is proportional to the Gleason score of the patients. While several compounds have been identified that target group-I PAKs and these are active in cells and mice, and while some inhibitors have entered human trials, as of yet, none have been FDA-approved. Probable reasons for this lack of translation include issues related to selectivity, specificity, stability, and efficacy resulting in side effects and/or lack of efficacy. In the current review, we describe the pathophysiology and current treatment guidelines of PCa, present group-I PAKs as a potential druggable target to treat mPCa patients, and discuss the various ATP-competitive and allosteric inhibitors of PAKs. We also discuss the development and testing of a nanotechnology-based therapeutic formulation of group-I PAK inhibitors and its significant potential advantages as a novel, selective, stable, and efficacious mPCa therapeutic over other PCa therapeutics in the pipeline.

PAK1 Is Involved in the Spindle Assembly during the First Meiotic Division in Porcine Oocytes

P21-activated kinase 1 (PAK1), as a member of the PAK family, has been implicated in various functions during somatic mitosis; however, less is known about its role during oocyte meiosis. Herein, we highlight the indispensable role of PAK1 in regulating spindle assembly and cell cycle progression during the first meiotic division of porcine oocytes. First, we found that the activated PAK1 expressed dynamically, and its subcellular localization was tightly associated with the spindle dynamics during meiosis in porcine oocytes. Specific inhibition of PAK1 activity by inhibitor targeting PAK1 activation-3 (IPA-3) led to impaired extrusion of the first polar body (PB1); with most of the IPA-3-treated oocytes arrested at germinal vesicle breakdown (GVBD) and subjected to failure of bipolar spindle formation. However, the adverse effects caused by IPA-3 on oocytes could be restored by reducing disulfide bonds between PAK1 and IPA-3 with dithiothreitol (DTT) treatment. Furthermore, the co-immunoprecipitation assay revealed that PAK1 interacted directly with Aurora A and transforming acidic coiled coil 3 (TACC3), providing an additional explanation for the similar localization of Aurora A and activated PAK1. Additionally, inhibiting the activity of PAK1 decreased the expression of p-Aurora A and p-TACC3; however, the reduced activity of Aurora A and TACC3 could be restored by DTT. In conclusion, PAK1 plays a crucial role in the proper assembly of the spindle during the first meiotic division of porcine oocytes, and the regulation of PAK1 is associated with its effects on p-Aurora A and p-TACC3 expression.