Regulation of huntingtin palmitoylation and its role in Huntington Diseases

2007 ◽  
Vol 30 (4) ◽  
pp. 99
Author(s):  
F BJ Young ◽  
M R Hayden
Keyword(s):  
Health Research ◽  
Neurodegenerative Disorder ◽  
Critical Role ◽  
Neuronal Cell ◽  
Causative Mutation ◽  
General Role ◽  
Wide Range ◽  
And Function

Huntington’s Disease (HD) is an autosomal dominant neurodegenerative disorder characterized by motor, cognitive, and psychiatric deficits and selective neuronal cell death. The causative mutation in HD is an expansion of the N-terminal polyglutamine tract in huntingtin (htt), which results in altered trafficking of mutant htt and enhanced toxicity to striatal neurons. Post-translational modification by the lipid palmitate has been shown to play a critical role in the trafficking and function of many proteins, including htt. It has been previously demonstrated that huntingtin-interacting protein 14 (HIP14) is a palmitoyl transferase that palmitoylates htt. Previous characterization of HIP14 demonstrated a reduced interaction with mutant htt resulting in reduced palmitoylation, suggesting that palmitoylation may play a role in the pathogenesis of HD. Most recently, we have identified cysteine 214 as a major site of htt palmitoylation in the N-terminus of htt, close to the site of polyglutamine expansion. It was demonstrated that mutation of this site, rendering htt palmitoylation-resistant, results in increased neuronal toxicity, enhanced inclusion formation, and in altered trafficking of htt. Remarkably, mutation of the palmitoylation site in wild type htt also resulted in enhanced toxicity similar to that seen in mutant htt. Together, these previous studies suggest a critical role of palmitoylation in htt trafficking and function. Based on this preliminary work, we are characterizing the enzymatic regulation of huntingtin palmitoylation. Exploring htt palmitoylation in a number of existing and new mouse models imparts key insights into how this process is regulated in vivo. We are also exploring the relationship between palmitoylation and other post-translational modifications of htt. These studies will lead to an understanding of the regulation of palmitoylation of huntingtin in vivo, as well as setting the precedent to understand the general role of palmitoylation in a wide range of other human diseases. Ultimately, this may lead to identification of new therapeutic targets and treatments for patients. F.B.J.Y. is supported by a Canadian Institutes of Health Research Walter and Jessie Boyd & Charles Scriver - Child and Family Research Institute - UBC MD/PhD Studentship Award. She also receives funding from the Michael Smith Foundation for Health Research as a Junior Trainee.

scholarly journals A proline-rich sequence unique to MEK1 and MEK2 is required for raf binding and regulates MEK function.

1995 ◽  
Vol 15 (10) ◽  
pp. 5214-5225 ◽  
Author(s):  
A D Catling ◽  
H J Schaeffer ◽  
C W Reuter ◽  
G R Reddy ◽  
M J Weber
Keyword(s):  
Protein Interactions ◽  
Critical Role ◽  
Phosphorylation Site ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Serum Stimulation ◽  
And Function

Mammalian MEK1 and MEK2 contain a proline-rich (PR) sequence that is absent both from the yeast homologs Ste7 and Byr1 and from a recently cloned activator of the JNK/stress-activated protein kinases, SEK1/MKK4. Since this PR sequence occurs in MEKs that are regulated by Raf family enzymes but is missing from MEKs and SEKs activated independently of Raf, we sought to investigate the role of this sequence in MEK1 and MEK2 regulation and function. Deletion of the PR sequence from MEK1 blocked the ability of MEK1 to associate with members of the Raf family and markedly attenuated activation of the protein in vivo following growth factor stimulation. In addition, this sequence was necessary for efficient activation of MEK1 in vitro by B-Raf but dispensable for activation by a novel MEK1 activator which we have previously detected in fractionated fibroblast extracts. Furthermore, we found that a phosphorylation site within the PR sequence of MEK1 was required for sustained MEK1 activity in response to serum stimulation of quiescent fibroblasts. Consistent with this observation, we observed that MEK2, which lacks a phosphorylation site at the corresponding position, was activated only transiently following serum stimulation. Finally, we found that deletion of the PR sequence from a constitutively activated MEK1 mutant rendered the protein nontransforming in Rat1 fibroblasts. These observations indicate a critical role for the PR sequence in directing specific protein-protein interactions important for the activation, inactivation, and downstream functioning of the MEKs.

scholarly journals Role of Exosomes in Islet Transplantation

2021 ◽  
Vol 12 ◽  
Author(s):  
Jordan Mattke ◽  
Srividya Vasu ◽  
Carly M. Darden ◽  
Kenjiro Kumano ◽  
Michael C. Lawrence ◽  
...  
Keyword(s):  
Islet Transplantation ◽  
Graft Function ◽  
Pancreatic Islet Transplantation ◽  
Complex Molecules ◽  
Wide Range ◽  
And Function ◽  
Antigen Presenting

Exosomes are known for their ability to transport nucleic acid, lipid, and protein molecules, which allows for communication between cells and tissues. The cargo of the exosomes can have a variety of effects on a wide range of targets to mediate biological function. Pancreatic islet transplantation is a minimally invasive cell replacement therapy to prevent or reverse diabetes mellitus and is currently performed in patients with uncontrolled type 1 diabetes or chronic pancreatitis. Exosomes have become a focus in the field of islet transplantation for the study of diagnostic markers of islet cell viability and function. A growing list of miRNAs identified from exosomes collected during the process of isolating islets can be used as diagnostic biomarkers of islet stress and damage, leading to a better understanding of critical steps of the isolation procedure that can be improved to increase islet yield and quality. Exosomes have also been implicated as a possible contributor to islet graft rejection following transplantation, as they carry donor major histocompatibility complex molecules, which are then processed by recipient antigen-presenting cells and sensed by the recipient immune cells. Exosomes may find their way into the therapeutic realm of islet transplantation, as exosomes isolated from mesenchymal stem cells have shown promising results in early studies that have seen increased viability and functionality of isolated and grafted islets in vitro as well as in vivo. With the study of exosomes still in its infancy, continued research on the role of exosomes in islet transplantation will be paramount to understanding beta cell regeneration and improving long-term graft function.

scholarly journals The immune-inflammatory response of oligodendrocytes in a murine model of preterm white matter injury: the role of TLR3 activation

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Marta Boccazzi ◽  
Juliette Van Steenwinckel ◽  
Anne-Laure Schang ◽  
Valérie Faivre ◽  
Tifenn Le Charpentier ◽  
...  
Keyword(s):  
White Matter ◽  
Primary Cultures ◽  
White Matter Injury ◽  
Poly I:C ◽  
Cytokines And Chemokines ◽  
Wide Range ◽  
Preterm Born ◽  
And Function

AbstractA leading cause of preterm birth is the exposure to systemic inflammation (maternal/fetal infection), which leads to neuroinflammation and white matter injury (WMI). A wide range of cytokines and chemokines are expressed and upregulated in oligodendrocytes (OLs) in response to inflammation and numerous reports show that OLs express several receptors for immune related molecules, which enable them to sense inflammation and to react. However, the role of OL immune response in WMI is unclear. Here, we focus our study on toll-like receptor-3 (TLR3) that is activated by double-strand RNA (dsRNA) and promotes neuroinflammation. Despite its importance, its expression and role in OLs remain unclear. We used an in vivo mouse model, which mimics inflammation-mediated WMI of preterm born infants consisting of intraperitoneal injection of IL-1β from P1 to P5. In the IL-1β-treated animals, we observed the upregulation of Tlr3, IL-1β, IFN-β, Ccl2, and Cxcl10 in both PDGFRα+ and O4+ sorted cells. This upregulation was higher in O4+ immature OLs (immOLs) as compared to PDGFRα+ OL precursor cells (OPCs), suggesting a different sensitivity to neuroinflammation. These observations were confirmed in OL primary cultures: cells treated with TLR3 agonist Poly(I:C) during differentiation showed a stronger upregulation of Ccl2 and Cxcl10 compared to cells treated during proliferation and led to decreased expression of myelin genes. Finally, OLs were able to modulate microglia phenotype and function depending on their maturation state as assessed by qPCR using validated markers for immunomodulatory, proinflammatory, and anti-inflammatory phenotypes and by phagocytosis and morphological analysis. These results show that during inflammation the response of OLs can play an autonomous role in blocking their own differentiation: in addition, the immune activation of OLs may play an important role in shaping the response of microglia during inflammation.

scholarly journals Thymosin β4 is essential for thrombus formation by controlling the G-actin/F-actin equilibrium in platelets

Haematologica ◽  
2021 ◽  
Author(s):  
Inga Scheller ◽  
Sarah Beck ◽  
Vanessa Göb ◽  
Carina Gross ◽  
Raluca A. I. Neagoe ◽  
...  
Keyword(s):  
Thrombus Formation ◽  
Critical Role ◽  
Actin Dynamics ◽  
Thymosin Β4 ◽  
Clot Retraction ◽  
And Function ◽  
External Signals

Coordinated rearrangements of the actin cytoskeleton are pivotal for platelet biogenesis from megakaryocytes (MKs) but also orchestrate key functions of peripheral platelets in hemostasis and thrombosis, such as granule release, the formation of filopodia and lamellipodia, or clot retraction. Along with profilin (Pfn) 1, thymosin β4 (encoded by Tmsb4x) is one of the two main G-actin sequestering proteins within cells of higher eukaryotes, and its intracellular concentration is particularly high in cells that rapidly respond to external signals by increased motility, such as platelets. Here, we analyzed constitutive Tmsb4x knockout (KO) mice to investigate the functional role of the protein in platelet production and function. Thymosin β4 deficiency resulted in a macrothrombocytopenia with only mildly increased platelet volume and an unaltered platelet life span. MK numbers in the bone marrow (BM) and spleen were unaltered, however, Tmsb4x KO MKs showed defective proplatelet formation in vitro and in vivo. Thymosin β4 deficient platelets displayed markedly decreased G-actin levels and concomitantly increased F-actin levels resulting in accelerated spreading on fibrinogen and clot retraction. Moreover, Tmsb4x KO platelets showed activation defects and an impaired immunoreceptor tyrosine-based activation motif (ITAM) signaling downstream of the activating collagen receptor glycoprotein (GP) VI. These defects translated into impaired aggregate formation under flow, protection from occlusive arterial thrombus formation in vivo and increased tail bleeding times. In summary, these findings point to a critical role of thymosin β4 for actin dynamics during platelet biogenesis, platelet activation downstream of GPVI and thrombus stability.

Flt3-Ligand Plays a Critical Role in Development and Function of CD8+/TCR− Facilitating Cells in Bone Marrow,

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4003-4003
Author(s):  
Yiming Huang ◽  
Thomas Miller ◽  
Hong Xu ◽  
Yujie Wen ◽  
Suzanne T Ildstad
Keyword(s):  
Bone Marrow ◽  
Critical Role ◽  
Flt3 Ligand ◽  
Wild Type ◽  
Graft Versus Host ◽  
Equity Ownership ◽  
Total Body ◽  
And Function

Abstract Abstract 4003 Graft facilitating cells (FC) are a CD8+/TCR− bone marrow subpopulation that enhance engraftment of purified hematopoietic cells (HSC) in allogeneic mouse recipients without causing graft-versus-host disease. They also enhance engraftment of suboptimal numbers of syngeneic HSC. FC induce antigen-specific CD4+/CD25+/FoxP3+ regulatory T cells in vivo. The major subpopulation in FC is resembles plasmacytoid precursor dendritic cells (p-preDC) both phenotypically and functionally. Treatment of mice with Flt3 ligand (FL) results in a significant increase in FC in peripheral blood (PB) and FL-expanded-PB FC enhanced HSC engraftment. In this study, we evaluated the role of FL in FC development using FL-KO mice. We first compared FC from FL-KO B6 mice with FC from B6 mice to evaluate the FC total cellular composition. The number of FC was significantly decreased in FL-KO mice compared to wild type controls (P = 0.0003). The number of p-preDC FC was also significantly decreased (P = 0.0001), suggesting that FL is important in the development of p-preDC FC. Next, we tested whether FL-KO FC facilitate engraftment of HSC in allogeneic recipients. FC were sorted from FL-KO B6 mice and HSC (C-Kit+/Sca-1+/Lin−) were sorted from B6 mice. 10,000 B6 HSC plus 30,000 FL-KO FC were transplanted into NOD recipients conditioned with 950 cGy of total body irradiation. Controls received 10,000 B6 HSC with or without 30,000 B6 FC. Only 36% (5 of 14) NOD recipients of B6 HSC alone engrafted and two mice survived up to 160 days (Figure). Sixty-three percent (5 of 8) of recipients transplanted with B6 HSC + FL-KO B6 FC engrafted and only one mouse survived up to 160 days. Seventy-five percent (9 of 12) recipients of B6 HSC + B6 FC engrafted and seven of the mice survived more than 160 days. The level of donor chimerism in recipients of B6 HSC + B6 FC (57% ± 10%) was significantly higher than recipients of B6 HSC + FL-KO B6 FC (14% ± 3%; P = 0.003) or B6 HSC alone (22% ± 6%; P = 0.005). These data demonstrate that FL-KO FC fail to facilitate durable allogeneic HSC engraftment, suggesting that flt3-ligand plays a critical role in development of functional FC. Disclosures: Ildstad: Regenerex, LLC: Equity Ownership.

Developing Brain and Heart Cells Respond Similarly to Altered Mechanical Loads

2010 ◽  
Author(s):  
Benjamen A. Filas ◽  
Philip V. Bayly ◽  
Larry A. Taber
Keyword(s):  
Critical Role ◽  
Congenital Defects ◽  
Heart Cells ◽  
Morphological Adaptation ◽  
Mechanical Loads ◽  
Mechanical Environment ◽  
And Function ◽  
Internal Pressures

Past studies have shown that the mechanical environment plays a critical role in regulating tissue development and function. For example, in the embryonic heart abnormal internal pressures cause morphological adaptation leading to aberrant morphogenesis [1]. Similarly, increasing luminal pressure in the early brain results in hyper-proliferation of the neuroepithelium [2]. Less is known, however, about how embryonic precursor cells quantitatively adapt to changes in loading, especially in vivo and across tissue types. These data would be valuable in determining the role of altered mechanical loads in congenital defects.

scholarly journals Knockdown of V-ATPase subunit A (atp6v1a) impairs acid secretion and ion balance in zebrafish (Danio rerio)

2007 ◽  
Vol 292 (5) ◽  
pp. R2068-R2076 ◽  
Author(s):  
Jiun-Lin Horng ◽  
Li-Yih Lin ◽  
Chang-Jen Huang ◽  
Fumi Katoh ◽  
Toyoji Kaneko ◽  
...  
Keyword(s):  
Acid Secretion ◽  
Apical Membrane ◽  
Critical Role ◽  
Ion Balance ◽  
Atpase Subunit ◽  
Subunit A ◽  
Acid Secreting ◽  
And Function

In the skin of zebrafish embryo, the vacuolar H+-ATPase (V-ATPase, H+ pump) distributed mainly in the apical membrane of H+-pump-rich cells, which pump internal acid out of the embryo and function similarly to acid-secreting intercalated cells in mammalian kidney. In addition to acid excretion, the electrogenic H+ efflux via the H+-ATPases in the gill apical membrane of freshwater fish was proposed to act as a driving force for Na+ entry through the apical Na+ channels. However, convincing molecular physiological evidence in vivo for this model is still lacking. In this study, we used morpholino-modified antisense oligonucleotides to knockdown the gene product of H+-ATPase subunit A ( atp6v1a) and examined the phenotype of the mutants. The H+-ATPase knockdown embryos revealed several abnormalities, including suppression of acid-secretion from skin, growth retardation, trunk deformation, and loss of internal Ca2+ and Na+. This finding reveals the critical role of H+-ATPase in embryonic acid -secretion and ion balance, as well.

scholarly journals Defect in Synaptic Vesicle Precursor Transport and Neuronal Cell Death in KIF1A Motor Protein–deficient Mice

1998 ◽  
Vol 141 (2) ◽  
pp. 431-441 ◽  
Author(s):  
Yoshiaki Yonekawa ◽  
Akihiro Harada ◽  
Yasushi Okada ◽  
Takeshi Funakoshi ◽  
Yoshimitsu Kanai ◽  
...  
Keyword(s):  
Cell Death ◽  
Synaptic Vesicle ◽  
Neuronal Degeneration ◽  
Critical Role ◽  
Neuronal Cell Death ◽  
Neuronal Cell ◽  
Organelle Transport ◽  
Murine Homologue ◽  
And Function

The nerve axon is a good model system for studying the molecular mechanism of organelle transport in cells. Recently, the new kinesin superfamily proteins (KIFs) have been identified as candidate motor proteins involved in organelle transport. Among them KIF1A, a murine homologue of unc-104 gene of Caenorhabditis elegans, is a unique monomeric neuron– specific microtubule plus end–directed motor and has been proposed as a transporter of synaptic vesicle precursors (Okada, Y., H. Yamazaki, Y. Sekine-Aizawa, and N. Hirokawa. 1995. Cell. 81:769–780). To elucidate the function of KIF1A in vivo, we disrupted the KIF1A gene in mice. KIF1A mutants died mostly within a day after birth showing motor and sensory disturbances. In the nervous systems of these mutants, the transport of synaptic vesicle precursors showed a specific and significant decrease. Consequently, synaptic vesicle density decreased dramatically, and clusters of clear small vesicles accumulated in the cell bodies. Furthermore, marked neuronal degeneration and death occurred both in KIF1A mutant mice and in cultures of mutant neurons. The neuronal death in cultures was blocked by coculture with wild-type neurons or exposure to a low concentration of glutamate. These results in cultures suggested that the mutant neurons might not sufficiently receive afferent stimulation, such as neuronal contacts or neurotransmission, resulting in cell death. Thus, our results demonstrate that KIF1A transports a synaptic vesicle precursor and that KIF1A-mediated axonal transport plays a critical role in viability, maintenance, and function of neurons, particularly mature neurons.

scholarly journals The role of Mfn2 in the structure and function of ER-mitochondrial tethering in vivo

2021 ◽  
Author(s):  
Song Han ◽  
Fanpeng Zhao ◽  
Jeffrey Hsia ◽  
Xiaopin Ma ◽  
Yi Liu ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Critical Role ◽  
Biochemical Changes ◽  
Conditional Knockout ◽  
Functional Studies ◽  
And Function ◽  
Close Contacts

The mitochondria-ER contacts (MERCs) plays an essential role in multiple cell physiological process. While Mfn2 was the first protein implicated in the formation of MERCs, it is debated whether it acts as a tether or antagonizer, largely based on in vitro studies. To understand the role of Mfn2 in MERCs in vivo, we characterized ultrastructural and biochemical changes of MERCs in pyramidal neurons of hippocampus in Mfn2 conditional knockout (KO) mice and in Mfn2 overexpression (OE) mice and found Mfn2 ablation caused reduced close contacts while Mfn2 OE caused increased close contacts between ER and mitochondria in vivo. Functional studies on SH-SY5Y cells with Mfn2 KO or overexpression demonstrating similar biochemical changes found that mitochondrial calcium uptake along with IP3R3-Grp75 interaction was decreased in Mfn2 KO cells but increased in the Mfn2 OE cells. Lastly, we found Mfn2 KO decreased and Mfn2 OE increased the interaction between the ER-mitochondria tethering pair of VAPB-PTPIP51. In conclusion, our study supports the notion that Mfn2 plays a critical role in ER-mitochondrial tethering and the formation of close contacts in neuronal cells in vivo.

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