Rab27a Is an Essential Component of Melanosome Receptor for Myosin Va

Melanocytes that lack the GTPase Rab27a (ashen) are disabled in myosin Va-dependent melanosome capture because the association of the myosin with the melanosome surface depends on the presence of this resident melanosomal membrane protein. One interpretation of these observations is that Rab27a functions wholly or in part as the melanosome receptor for myosin Va (Myo5a). Herein, we show that the ability of the myosin Va tail domain to localize to the melanosome and generate a myosin Va null (dilute) phenotype in wild-type melanocytes is absolutely dependent on the presence of exon F, one of two alternatively spliced exons present in the tail of the melanocyte-spliced isoform of myosin Va but not the brain-spliced isoform. Exon D, the other melanocyte-specific tail exon, is not required. Similarly, the ability of full-length myosin Va to colocalize with melanosomes and to rescue their distribution indilute melanocytes requires exon F but not exon D. These results predict that an interaction between myosin Va and Rab27a should be exon F dependent. Consistent with this, Rab27a present in detergent lysates of melanocytes binds to beads coated with purified, full-length melanocyte myosin Va and melanocyte myosin Va lacking exon D, but not to beads coated with melanocyte myosin Va lacking exon F or brain myosin Va. Moreover, the preparation of melanocyte lysates in the presence of GDP rather than guanosine-5′-O-(3-thio)triphosphate reduces the amount of Rab27a bound to melanocyte myosin Va-coated beads by approximately fourfold. Finally, pure Rab27a does not bind to myosin Va-coated beads, suggesting that these two proteins interact indirectly. Together, these results argue that Rab27a is an essential component of a protein complex that serves as the melanosome receptor for myosin Va, suggest that this complex contains at least one additional protein capable of bridging the indirect interaction between Rab27a and myosin Va, and imply that the recruitment of myosin Va to the melanosome surface in vivo should be regulated by factors controlling the nucleotide state of Rab27a.

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Replacement of the Ectodomains of the Hemagglutinin-Neuraminidase and Fusion Glycoproteins of Recombinant Parainfluenza Virus Type 3 (PIV3) with Their Counterparts from PIV2 Yields Attenuated PIV2 Vaccine Candidates

Journal of Virology ◽

10.1128/jvi.74.14.6448-6458.2000 ◽

2000 ◽

Vol 74 (14) ◽

pp. 6448-6458 ◽

Cited By ~ 31

Author(s):

Tao Tao ◽

Mario H. Skiadopoulos ◽

Fatemeh Davoodi ◽

Jeffrey M. Riggs ◽

Peter L. Collins ◽

...

Keyword(s):

Virus Type ◽

Vaccine Candidate ◽

Cytoplasmic Tail ◽

Full Length ◽

Parainfluenza Virus ◽

Tail Domain ◽

Wild Type ◽

Vaccine Candidates

ABSTRACT We sought to develop a live attenuated parainfluenza virus type 2 (PIV2) vaccine strain for use in infants and young children, using reverse genetic techniques that previously were used to rapidly produce a live attenuated PIV1 vaccine candidate. The PIV1 vaccine candidate, designated rPIV3-1cp45, was generated by substituting the full-length HN and F proteins of PIV1 for those of PIV3 in the attenuatedcp45 PIV3 vaccine candidate (T. Tao et al., J. Virol. 72:2955–2961, 1998; M. H. Skiadopoulos et al., Vaccine 18:503–510, 1999). However, using the same strategy, we failed to recover recombinant chimeric PIV3-PIV2 isolate carrying the full-length PIV2 glycoproteins in a wild-type PIV3 backbone. Viable PIV3-PIV2 chimeras were recovered when chimeric HN and F open reading frames (ORFs) rather than complete PIV2 F and HN ORFs were used to construct the full-length cDNA. The recovered viruses, designated rPIV3-2CT, in which the PIV2 ectodomain and transmembrane domain were fused to the PIV3 cytoplasmic domain, and rPIV3-2TM, in which the PIV2 ectodomain was fused to the PIV3 transmembrane and cytoplasmic tail domain, possessed similar in vitro and in vivo phenotypes. Thus, it appeared that only the cytoplasmic tail of the HN or F glycoprotein of PIV3 was required for successful recovery of PIV3-PIV2 chimeras. Although rPIV3-2CT and rPIV3-2TM replicated efficiently in vitro, they were moderately to highly attenuated for replication in the respiratory tracts of hamsters, African green monkeys (AGMs), and chimpanzees. This unexpected finding indicated that chimerization of the HN and F proteins of PIV2 and PIV3 itself specified an attenuation phenotype in vivo. Despite this attenuation, these viruses were highly immunogenic and protective against challenge with wild-type PIV2 in hamsters and AGMs, and they represent promising candidates for clinical evaluation as a vaccine against PIV2. These chimeric viruses were further attenuated by the addition of 12 mutations of PIV3cp45 which lie outside of the HN and F genes. The attenuating effects of these mutations were additive with that of the chimerization, and thus inclusion of all or some of the cp45 mutations provides a means to further attenuate the PIV3-PIV2 chimeric vaccine candidates if necessary.

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Visualization of Melanosome Dynamics within Wild-Type and Dilute Melanocytes Suggests a Paradigm for Myosin V Function In Vivo

The Journal of Cell Biology ◽

10.1083/jcb.143.7.1899 ◽

1998 ◽

Vol 143 (7) ◽

pp. 1899-1918 ◽

Cited By ~ 295

Author(s):

Xufeng Wu ◽

Blair Bowers ◽

Kang Rao ◽

Qin Wei ◽

John A. Hammer

Keyword(s):

Wild Type Mouse ◽

Time Lapse ◽

Tail Domain ◽

Wild Type ◽

Myosin V ◽

Transport Models ◽

Myosin Va ◽

Cortical Shell ◽

Mutant Phenotypes

Unlike wild-type mouse melanocytes, where melanosomes are concentrated in dendrites and dendritic tips, melanosomes in dilute (myosin Va−) melanocytes are concentrated in the cell center. Here we sought to define the role that myosin Va plays in melanosome transport and distribution. Actin filaments that comprise a cortical shell running the length of the dendrite were found to exhibit a random orientation, suggesting that myosin Va could drive the outward spreading of melanosomes by catalyzing random walks. In contrast to this mechanism, time lapse video microscopy revealed that melanosomes undergo rapid (∼1.5 μm/s) microtubule-dependent movements to the periphery and back again. This bidirectional traffic occurs in both wild-type and dilute melanocytes, but it is more obvious in dilute melanocytes because the only melanosomes in their periphery are those undergoing this movement. While providing an efficient means to transport melanosomes to the periphery, this component does not by itself result in their net accumulation there. These observations, together with previous studies showing extensive colocalization of myosin Va and melanosomes in the actin-rich periphery, suggest a mechanism in which a myosin Va–dependent interaction of melanosomes with F-actin in the periphery prevents these organelles from returning on microtubules to the cell center, causing their distal accumulation. This “capture” model is supported by the demonstration that (a) expression of the myosin Va tail domain within wild-type cells creates a dilute-like phenotype via a process involving initial colocalization of tail domains with melanosomes in the periphery, followed by an ∼120-min, microtubule-based redistribution of melanosomes to the cell center; (b) microtubule-dependent melanosome movement appears to be damped by myosin Va; (c) intermittent, microtubule-independent, ∼0.14 μm/s melanosome movements are seen only in wild-type melanocytes; and (d) these movements do not drive obvious spreading of melanosomes over 90 min. We conclude that long-range, bidirectional, microtubule-dependent melanosome movements, coupled with actomyosin Va–dependent capture of melanosomes in the periphery, is the predominant mechanism responsible for the centrifugal transport and peripheral accumulation of melanosomes in mouse melanocytes. This mechanism represents an alternative to straightforward transport models when interpreting other myosin V mutant phenotypes.

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DJ-1 regulates the integrity and function of ER-mitochondria association through interaction with IP3R3-Grp75-VDAC1

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1906565116 ◽

2019 ◽

Vol 116 (50) ◽

pp. 25322-25328 ◽

Cited By ~ 20

Author(s):

Yi Liu ◽

Xiaopin Ma ◽

Hisashi Fujioka ◽

Jun Liu ◽

Shengdi Chen ◽

...

Keyword(s):

Autosomal Recessive ◽

Cellular Mechanism ◽

Loss Of Function ◽

Wild Type ◽

Calcium Efflux ◽

And Function ◽

The Brain ◽

Early Onset Parkinson’S Disease

Loss-of-function mutations in DJ-1 are associated with autosomal recessive early onset Parkinson’s disease (PD), yet the underlying pathogenic mechanism remains elusive. Here we demonstrate that DJ-1 localized to the mitochondria-associated membrane (MAM) both in vitro and in vivo. In fact, DJ-1 physically interacts with and is an essential component of the IP3R3-Grp75-VDAC1 complexes at MAM. Loss of DJ-1 disrupted the IP3R3-Grp75-VDAC1 complex and led to reduced endoplasmic reticulum (ER)-mitochondria association and disturbed function of MAM and mitochondria in vitro. These deficits could be rescued by wild-type DJ-1 but not by the familial PD-associated L166P mutant which had demonstrated reduced interaction with IP3R3-Grp75. Furthermore, DJ-1 ablation disturbed calcium efflux-induced IP3R3 degradation after carbachol treatment and caused IP3R3 accumulation at the MAM in vitro. Importantly, similar deficits in IP3R3-Grp75-VDAC1 complexes and MAM were found in the brain of DJ-1 knockout mice in vivo. The DJ-1 level was reduced in the substantia nigra of sporadic PD patients, which was associated with reduced IP3R3-DJ-1 interaction and ER-mitochondria association. Together, these findings offer insights into the cellular mechanism in the involvement of DJ-1 in the regulation of the integrity and calcium cross-talk between ER and mitochondria and suggests that impaired ER-mitochondria association could contribute to the pathogenesis of PD.

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Expression and Functional Assessment of an Alternatively Spliced Extracellular Ca2+-Sensing Receptor in Growth Plate Chondrocytes

Endocrinology ◽

10.1210/en.2005-0256 ◽

2005 ◽

Vol 146 (12) ◽

pp. 5294-5303 ◽

Cited By ~ 55

Author(s):

Luis Rodriguez ◽

Chialing Tu ◽

Zhiqiang Cheng ◽

Tsui-Hua Chen ◽

Daniel Bikle ◽

...

Keyword(s):

Cell Surface ◽

Growth Plate ◽

Inositol Phosphate ◽

Intact Cell ◽

Chinese Hamster ◽

Full Length ◽

Wild Type ◽

Growth Plate Chondrocytes ◽

Matrix Gene ◽

Alternatively Spliced

The extracellular Ca2+-sensing receptor (CaR) plays an essential role in mineral homeostasis. Studies to generate CaR-knockout (CaR−/−) mice indicate that insertion of a neomycin cassette into exon 5 of the mouse CaR gene blocks the expression of full-length CaRs. This strategy, however, allows for the expression of alternatively spliced CaRs missing exon 5 [Exon5(−)CaRs]. These experiments addressed whether growth plate chondrocytes (GPCs) from CaR−/− mice express Exon5(−)CaRs and whether these receptors activate signaling. RT-PCR and immunocytochemistry confirmed the expression of Exon5(−)CaR in growth plates from CaR−/− mice. In Chinese hamster ovary or human embryonic kidney-293 cells, recombinant human Exon5(−)CaRs failed to activate phospholipase C likely due to their inability to reach the cell surface as assessed by intact-cell ELISA and immunocytochemistry. Human Exon5(−)CaRs, however, trafficked normally to the cell surface when overexpressed in wild-type or CaR−/− GPCs. Immunocytochemistry of growth plate sections and cultured GPCs from CaR−/− mice showed easily detectable cell-membrane expression of endogenous CaRs (presumably Exon5(−)CaRs), suggesting that trafficking of this receptor form to the membrane can occur in GPCs. In GPCs from CaR−/− mice, high extracellular [Ca2+] ([Ca2+]e) increased inositol phosphate production with a potency comparable with that of wild-type GPCs. Raising [Ca2+]e also promoted the differentiation of CaR−/− GPCs as indicated by changes in proteoglycan accumulation, mineral deposition, and matrix gene expression. Taken together, our data support the idea that expression of Exon5(−)CaRs may compensate for the loss of full-length CaRs and be responsible for sensing changes in [Ca2+]e in GPCs in CaR−/− mice.

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GAGA Factor Isoforms Have Distinct but Overlapping Functions In Vivo

Molecular and Cellular Biology ◽

10.1128/mcb.21.24.8565-8574.2001 ◽

2001 ◽

Vol 21 (24) ◽

pp. 8565-8574 ◽

Cited By ~ 20

Author(s):

Anthony J. Greenberg ◽

Paul Schedl

Keyword(s):

Fusion Protein ◽

Transcriptional Activation ◽

Functional Difference ◽

Wild Type ◽

Gaga Factor ◽

Phenotypic Analysis ◽

Alternatively Spliced

ABSTRACT The Drosophila melanogaster GAGA factor (encoded by the Trithorax-like [Trl] gene) is required for correct chromatin architecture at diverse chromosomal sites. The Trl gene encodes two alternatively spliced isoforms of the GAGA factor (GAGA-519 and GAGA-581) that are identical except for the length and sequence of the C-terminal glutamine-rich (Q) domain. In vitro and tissue culture experiments failed to find any functional difference between the two isoforms. We made a set of transgenes that constitutively express cDNAs coding for either of the isoforms with the goal of elucidating their roles in vivo. Phenotypic analysis of the transgenes in Trl mutant background led us to the conclusion that GAGA-519 and GAGA-581 perform different, albeit largely overlapping, functions. We also expressed a fusion protein with LacZ disrupting the Q domain of GAGA-519. This LacZ fusion protein compensated for the loss of wild-type GAGA factor to a surprisingly large extent. This suggests that the Q domain either is not required for the essential functions performed by the GAGA protein or is exclusively used for tetramer formation. These results are inconsistent with a major role of the Q domain in chromatin remodeling or transcriptional activation. We also found that GAGA-LacZ was able to associate with sites not normally occupied by the GAGA factor, pointing to a role of the Q domain in binding site choice in vivo.

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Endothelial cell-specific reduction of heparan sulfate suppresses glioma growth in mice

Discover Oncology ◽

10.1007/s12672-021-00444-3 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Takamasa Kinoshita ◽

Hiroyuki Tomita ◽

Hideshi Okada ◽

Ayumi Niwa ◽

Fuminori Hyodo ◽

...

Keyword(s):

Endothelial Cell ◽

Heparan Sulfate ◽

Vascular Endothelium ◽

Wild Type ◽

Brain Capillaries ◽

Gene Encoding ◽

Glioma Growth ◽

Underlying Mechanisms ◽

The Brain

Abstract Purpose Heparan sulfate (HS) is one of the factors that has been suggested to be associated with angiogenesis and invasion of glioblastoma (GBM), an aggressive and fast-growing brain tumor. However, it remains unclear how HS of endothelial cells is involved in angiogenesis in glioblastoma and its prognosis. Thus, we investigated the effect of endothelial cell HS on GBM development. Methods We generated endothelial cell-specific knockout of Ext1, a gene encoding a glycosyltransferase and essential for HS synthesis, and murine GL261 glioblastoma cells were orthotopically transplanted. Two weeks after transplantation, we examined the tumor progression and underlying mechanisms. Results The endothelial cell-specific Ext1 knockout (Ext1CKO) mice exhibited reduced HS expression specifically in the vascular endothelium of the brain capillaries compared with the control wild-type (WT) mice. GBM growth was significantly suppressed in Ext1CKO mice compared with that in WT mice. After GBM transplantation, the survival rate was significantly higher in Ext1CKO mice than in WT mice. We investigated how the effect of fibroblast growth factor 2 (FGF2), which is known as an angiogenesis-promoting factor, differs between Ext1CKO and WT mice by using an in vivo Matrigel assay and demonstrated that endothelial cell-specific HS reduction attenuated the effect of FGF2 on angiogenesis. Conclusions HS reduction in the vascular endothelium of the brain suppressed GBM growth and neovascularization in mice.

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SUN-260 Dual Role of Carboxypeptidase E in Prohormone Processing and a Novel Neurotrophic Factor Mediating Neuroprotection and Cognitive Functions in Hippocampal CA3 Neurons in Mice

Journal of the Endocrine Society ◽

10.1210/jendso/bvaa046.100 ◽

2020 ◽

Vol 4 (Supplement_1) ◽

Author(s):

Lan Xiao ◽

Vinay Sharma ◽

Leila Toulabi ◽

Xuyu Yang ◽

Cheol Lee ◽

...

Keyword(s):

Neurotrophic Factor ◽

Neuronal Degeneration ◽

Tyrosine Kinase Receptor ◽

Wild Type ◽

Prohormone Processing ◽

Hippocampal Ca3 ◽

Ca3 Neurons ◽

The Brain

Abstract Stress causes release of glucocorticoids from the adrenals which then circulate to the brain. High concentrations glucocorticoid from chronic severe stress results in pathophysiology in the brain, including neuronal degeneration, cell death and cognitive dysfunction, leading to diseases such as Alzheimer Disease and Major Depressive Disorders. Neurotrophic/growth factors such as BDNF, NGF and NT3 have been linked to these pathological conditions. Carboxypeptidase E (CPE), a proneuropeptide/prohormone processing enzyme, also named neurotrophic factor-α1(NFα1) is highly expressed in the stress-vulnerable hippocampal CA3 neurons, and was shown to have neuroprotective activity from in vitro studies. Here we investigated if CPE-NFα1 functions in vivo, independent of its enzymatic activity, and the mechanism underlying its action. We generated knock-in mice expressing a non-enzymatic form of CPE, CPE-E342Q, but not wild-type CPE. The CPE-E342Q mice showed significantly decreased neuropeptide content and exhibited obesity, diabetes and infertility due to lack of prohormone processing activity, similar to CPE-KO mice. However, they showed no hippocampal CA3 degeneration, exhibited neurogenesis in the dentate gyrus, and displayed normal spatial learning and memory, similar to CPE wild-type mice, after weaning stress; unlike CPE-KO mice which showed hippocampal CA3 neuronal degeneration and cognitive deficits. Binding studies showed that radiolabeled CPE bound hippocampal cell membrane specifically, in a saturable manner. Binding of CPE and CPE-E342Q to hippocampal neurons activated Erk signaling and pre-treatment with either of these proteins protected neurons against H2O2- or glutamate-induced neurotoxcity by increasing BCL2 expression. In vitro and in vivo inhibitor studies demonstrated that this neuroprotective effect was independent of tyrosine kinase receptor signaling. Taken together, the data provide evidence that CPE-NFα1 is a unique neurotrophic factor which acts through a non-tyrosine kinase receptor to activate Erk-BCL2 signaling to protect hippocampal CA3 neurons against stress-induced neurodegeneration and maintaining normal cognitive functions in mice.

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Influence of Intron Length on Alternative Splicing of CD44

Molecular and Cellular Biology ◽

10.1128/mcb.18.10.5930 ◽

1998 ◽

Vol 18 (10) ◽

pp. 5930-5941 ◽

Cited By ~ 49

Author(s):

Martyn V. Bell ◽

Alison E. Cowper ◽

Marie-Paule Lefranc ◽

John I. Bell ◽

Gavin R. Screaton

Keyword(s):

Alternative Splicing ◽

Genomic Structure ◽

Single Gene ◽

Intron Length ◽

Protein Isoforms ◽

Major Influence ◽

Eukaryotic Genes ◽

Alternatively Spliced ◽

Alternatively Spliced Exons

ABSTRACT Although the splicing of transcripts from most eukaryotic genes occurs in a constitutive fashion, some genes can undergo a process of alternative splicing. This is a genetically economical process which allows a single gene to give rise to several protein isoforms by the inclusion or exclusion of sequences into or from the mature mRNA. CD44 provides a unique example; more than 1,000 possible isoforms can be produced by the inclusion or exclusion of a central tandem array of 10 alternatively spliced exons. Certain alternatively spliced exons have been ascribed specific functions; however, independent regulation of the inclusion or skipping of each of these exons would clearly demand an extremely complex regulatory network. Such a network would involve the interaction of many exon-specific trans-acting factors with the pre-mRNA. Therefore, to assess whether the exons are indeed independently regulated, we have examined the alternative exon content of a large number of individual CD44 cDNA isoforms. This analysis shows that the downstream alternatively spliced exons are favored over those lying upstream and that alternative exons are often included in blocks rather than singly. Using a novel in vivo alternative splicing assay, we show that intron length has a major influence upon the alternative splicing of CD44. We propose a kinetic model in which short introns may overcome the poor recognition of alternatively spliced exons. These observations suggest that for CD44, intron length has been exploited in the evolution of the genomic structure to enable tissue-specific patterns of splicing to be maintained.

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Ott1(Rbm15) Regulates Thpo Response In HSCs Through Epigenetic Modifications Directing Alternative Splicing Of C-Mpl

Blood ◽

10.1182/blood.v122.21.222.222 ◽

2013 ◽

Vol 122 (21) ◽

pp. 222-222

Author(s):

Nan Xiao ◽

Kayla Morlock ◽

Jonathan L Jesneck ◽

Glen D Raffel

Keyword(s):

Bone Marrow ◽

Alternative Splicing ◽

Histone Acetylation ◽

Epigenetic Modifications ◽

Class I ◽

Fusion Partner ◽

Wild Type ◽

Hematopoietic Stem ◽

Alternatively Spliced

Abstract Thrombopoietin (Thpo), through its receptor c-Mpl, is essential for Hematopoietic Stem Cell (HSC) function and has a dose-dependent effect in which low concentrations promote quiescence and self-renewal in contrast to high Thpo concentrations which promote proliferation. Thpo production is largely stable in vivo, therefore it is unclear how this dual response is evoked physiologically. HSCs deleted for c-Mpl are unable to tolerate proliferative stress. Ott1(Rbm15), the 5’ fusion partner in t(1;22) acute megakaryocytic leukemia, is also essential for maintaining HSC quiescence during proliferative stress, however the mechanism has not been elucidated. Total c-Mpl expression in Ott1-deleted HSCs does not significantly differ from wild type, however, the existence of a cross-species, conserved isoform, Mpl-TR, with dominant negative activity, suggests a potential mechanism for affecting c-Mpl signaling via alternative splicing. Ott1 is a spliceosome component, is implicated in RNA processing and possesses RNA Recognition Motifs, yet has not been linked with any known physiologic targets. Analysis of c-Mpl isoforms in HSC-containing Lin-Sca1+c-Kit+ fractions and fetal liver megakaryocytes showed a marked increase in the ratio of Mpl-TR transcript. Ott1-deleted HSC populations displayed reduced Stat5 phosphorylation in response to Thpo stimulation consistent with decreased Mpl signaling. Exogenous expression of Mpl-TR in wild type bone marrow dramatically reduced short and long term engraftment into irradiated recipients, confirming in vivo activity of Mpl-TR in HSCs. To determine whether Ott1 complexes with Mpl RNA, RNA-immunoprecipitation was performed using an HA-tagged Ott1 and revealed complex formation with Mpl RNA. Alternative splicing is frequently regulated through a co-transcriptional mechanism utilizing local epigenetic modifications including histone acetylation and H3K4me3 marks. Ott1 was previously shown to bind class I Histone deacetylases (Hdacs) and the histone H3K4 methyl-transferase (HMT), Setd1b. To establish whether Ott1 interacts with the c-Mpl gene, Chromatin-immunoprecipitation (ChIP) using HA-tagged Ott1 was performed and found binding within regions flanking the alternatively spliced exons. ChIP using anti-pan-acetyl-H4 in Ott1 knockout Lin- bone marrow showed increased histone acetylation in the region shown to bind Ott1 compared to wild type. Conversely, ChIP using anti-H3K4me3 in the Ott1 knockout showed decreased H3K4me3 at the site of Ott1 binding consistent with loss of Ott1-associated Hdac and HMT activity. To test the functional consequences on splicing, treatment of wild type cells with either a class I Hdac inhibitor or a HMT inhibitor was able to significantly increase the ratio of Mpl-TR isoform. In summary, Ott1 regulates the production of the alternatively spliced c-Mpl isoform, Mpl-TR, and consequently Thpo response in HSCs. Mpl-TR expression impairs physiologic HSC function for long and short term engraftment. Ott1 complexes with c-Mpl RNA and chromatin adjacent to the exons alternatively spliced in the Mpl-TR isoform and regulates histone acetylation and methylation marks associated with splice decision. Therefore, Ott1-mediated alternative splicing of Mpl may provide a novel mechanism via chromatin modification for modulating HSC maintenance and proliferation in response to Thpo. Furthermore, the ability to control Mpl alternative splicing through epigenetic inhibitors opens unique possibilities for pharmacologically manipulating HSC function in vitro or in vivo. Disclosures: No relevant conflicts of interest to declare.

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Deletion of the Brain-Specific α and δ Isoforms of Adapter Protein SH2B1 Protects Mice From Obesity

10.2337/figshare.13229090.v2 ◽

2020 ◽

Author(s):

Jessica L. Cote ◽

Lawrence S. Argetsinger ◽

Anabel Flores ◽

Alan C. Rupp ◽

Joel M. Cline ◽

...

Keyword(s):

Energy Balance ◽

Adapter Protein ◽

Wild Type ◽

Leptin Sensitivity ◽

High Fat Diets ◽

Independent Mechanism ◽

Alternatively Spliced ◽

Fat Diets ◽

The Brain ◽

Inactivating Mutations

Mice lacking SH2B1 and humans with inactivating mutations of SH2B1 display severe obesity and insulin resistance. SH2B1 is an adapter protein that is recruited to the receptors of multiple hormones and neurotrophic factors. Of the four known alternatively-spliced SH2B1 isoforms, SH2B1b and SH2B1g exhibit ubiquitous expression, whereas SH2B1a and SH2B1d are essentially restricted to the brain. To understand the roles for SH2B1a and SH2B1d in energy balance and glucose metabolism, we generated mice lacking these brain-specific isoforms (adKO mice). adKO mice exhibit decreased food intake, protection from weight gain on standard and high fat diets, and an adiposity-dependent improvement in glucose homeostasis. SH2B1 has been suggested to impact energy balance via the modulation of leptin action. However, adKO mice exhibit leptin sensitivity that is similar to that of wild-type mice by multiple measures. Thus, decreasing the abundance of SH2B1a and/or SH2B1d relative to the other SH2B1 isoforms likely shifts energy balance towards a lean phenotype via a primarily leptin-independent mechanism. Our findings suggest that the different alternatively-spliced isoforms of SH2B1 perform different functions in vivo.

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