Dispensable role of Drosophila ortholog of LRRK2 kinase activity in survival of dopaminergic neurons

<p>Abstract</p> <p>Background</p> <p>Parkinson's disease (PD) is the most prevalent incurable neurodegenerative movement disorder. Mutations in <it>LRRK2 </it>are associated with both autosomal dominant familial and sporadic forms of PD. <it>LRRK2 </it>encodes a large putative serine/threonine kinase with GTPase activity. Increased LRRK2 kinase activity plays a critical role in pathogenic LRRK2 mutant-induced neurodegeneration <it>in vitro</it>. Little is known about the physiological function of LRRK2.</p> <p>Results</p> <p>We have recently identified a <it>Drosophila </it>line with a P-element insertion in an ortholog gene of human <it>LRRK2 </it>(<it>dLRRK</it>). The insertion results in a truncated <it>Drosophila </it>LRRK variant with N-terminal 1290 amino acids but lacking C-terminal kinase domain. The homozygous mutant fly develops normally with normal life span as well as unchanged number and pattern of dopaminergic neurons. However, <it>dLRRK </it>mutant flies were selectively sensitive to hydrogen peroxide induced stress but not to paraquat, rotenone and β-mercaptoethanol induced stresses.</p> <p>Conclusion</p> <p>Our results indicate that inactivation of <it>d</it>LRRK kinase activity is not essential for fly development and suggest that inhibition of LRRK activity may serve as a potential treatment of PD. However, <it>d</it>LRRK kinase activity likely plays a role in protecting against oxidative stress.</p

The Wingless Signaling Pathway Is Directly Involved inDrosophilaHeart Development

AbstractHeart development in both vertebrates andDrosophilais initiated by bilaterally symmetrical primordia that may be of equivalent embryological origin: the anterior lateral plate mesoderm in vertebrates and the dorsal-most mesoderm in arthropods. These mesodermal progenitors then merge into a heart tube at the ventral midline (vertebrates) or the dorsal midline (Drosophila). These observations suggest that there may be similarities between vertebrate and invertebrate heart development. The homeobox gene,tinman,is required for heart as well as visceral mesoderm formation inDrosophila,and at least one of several vertebrate genes with similarities in protein sequence and cardiac expression totinmanis crucial for heart development in vertebrates. Inductive signals are also required forDrosophilaheart development: The secreted gene product ofwingless(wg) is critical for heart development during a time period distinct from its function in segmentation and neurogenesis. Here, we show thatwgis epistatic to hedgehog (hh), another secreted segmentation gene product, in its requirement for heart formation. We also provide evidence show that downstream ofwgin the signal transduction cascade,dishevelled(dsh,a pioneer protein) andarmadillo(arm, β-catenin homolog) are mediating the cardiogenic Wg signal. In particular, overexpression ofdshcan restore heart formation in the absence ofwgfunction. We discuss the possibility that Wg signaling is part of a combinatorial mechanism to specify the cardiac mesoderm

d4eBP acts downstream of both dTOR and dFoxo to modulate cardiac functional aging in Drosophila

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75079/1/ACEL_504_sm_FigS1_TableS1-S2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/75079/2/j.1474-9726.2009.00504.x.pd

Characterization and developmental expression of AmphiNk2-2 , an NK2 class homeobox gene from amphioxus (Phylum Chordata; Subphylum Cephalochordata)

 The genome of amphioxus includes AmphiNk2-2 , the first gene of the NK2 homeobox class to be demonstrated in any invertebrate deuterostome. AmphiNk2-2 encodes a protein with a TN domain, homeodomain, and NK2-specific domain; on the basis of amino acid identities in these conserved regions, AmphiNk2-2 is a homolog of Drosophila vnd and vertebrate Nkx2–2. During amphioxus development, expression of Amph- iNk2-2 is first detected ventrally in the endoderm of late gastrulae. In neurulae, endodermal expression divides into three domains (the pharynx, midgut, and hindgut), and neural expression commences in two longitudinal bands of cells in the anterior neural tube. These neural tube cells occupy a ventrolateral position on either side of the cerebral vesicle (the probable homolog of the vertebrate diencephalic forebrain). The dynamic expression patterns of AmphiNkx2-2 suggest successive roles, first in regionalizing the endoderm and nervous system and later during differentiation of specific cell types in the gut (possibly peptide endocrine cells) and brain (possibly including axon outgrowth and guidance).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42246/1/427-208-2-100_82080100.pd

TGFB-INHB/activin signaling regulates age-dependent autophagy and cardiac health through inhibition of MTORC2 Autophagy

Age-related impairment of macroautophagy/autophagy and loss of cardiac tissue homeostasis contribute significantly to cardiovascular diseases later in life. MTOR (mechanistic target of rapamycin kinase) signaling is the most well-known regulator of autophagy, cellular homeostasis, and longevity. The MTOR signaling consists of two structurally and functionally distinct multiprotein complexes, MTORC1 and MTORC2. While MTORC1 is well characterized but the role of MTORC2 in aging and autophagy remains poorly understood. Here we identified TGFB-INHB/activin signaling as a novel upstream regulator of MTORC2 to control autophagy and cardiac health during aging. Using Drosophila heart as a model system, we show that cardiac-specific knockdown of TGFB-INHB/activin-like protein daw induces autophagy and alleviates age-related heart dysfunction, including cardiac arrhythmias and bradycardia. Interestingly, the downregulation of daw activates TORC2 signaling to regulate cardiac autophagy. Activation of TORC2 alone through overexpressing its subunit protein rictor promotes autophagic flux and preserves cardiac function with aging. In contrast, activation of TORC1 does not block autophagy induction in daw knockdown flies. Lastly, either daw knockdown or rictor overexpression in fly hearts prolongs lifespan, suggesting that manipulation of these pathways in the heart has systemic effects on longevity control. Thus, our studies discover the TGFB-INHB/activin-mediated inhibition of TORC2 as a novel mechanism for age-dependent decreases in autophagic activity and cardiac health

Sequence and developmental expression of amphioxus AmphiNk2–1 : insights into the evolutionary origin of the vertebrate thyroid gland and forebrain

 We characterized an amphioxus NK-2 homeobox gene ( AmphiNk2–1 ), a homologue of vertebrate Nkx2–1 , which is involved in the development of the central nervous system and thyroid gland. At the early neurula stage of amphioxus, AmphiNk2–1 expression is first detected medially in the neural plate. By the mid-neurula stage, expression is localized ventrally in the nerve cord and also begins in the endoderm. During the late neurula stage, the ventral neural expression becomes transiently segmented posteriorly and is then down-regulated except in the cerebral vesicle at the anterior end of the central nervous system. Within the cerebral vesicle AmphiNk2–1 is expressed in a broad ventral domain, probably comprising both the floor plate and basal plate regions; this pattern is comparable to Nkx2–1 expression in the mouse diencephalon. In the anterior part of the gut, expression becomes intense in the endostyle (the right wall of the pharynx), which is the presumed homologue of the vertebrate thyroid gland. More posteriorly, there is transitory expression in the midgut and hindgut. In sum, the present results help to support homologies (1) between the amphioxus endostyle and the vertebrate thyroid gland and (2) between the amphioxus cerebral vesicle and the vertebrate diencephalic forebrain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42247/1/427-209-4-254_92090254.pd

Survival response to increased ceramide involves metabolic adaptation through novel regulators of glycolysis and lipolysis

The sphingolipid ceramide elicits several stress responses, however, organisms survive despite increased ceramide but how they do so is poorly understood. We demonstrate here that the AKT/FOXO pathway regulates survival in increased ceramide environment by metabolic adaptation involving changes in glycolysis and lipolysis through novel downstream targets. We show that ceramide kinase mutants accumulate ceramide and this leads to reduction in energy levels due to compromised oxidative phosphorylation. Mutants show increased activation of Akt and a consequent decrease in FOXO levels. These changes lead to enhanced glycolysis by upregulating the activity of phosphoglyceromutase, enolase, pyruvate kinase, and lactate dehydrogenase to provide energy. A second major consequence of AKT/FOXO reprogramming in the mutants is the increased mobilization of lipid from the gut through novel lipase targets, CG8093 and CG6277 for energy contribution. Ubiquitous reduction of these targets by knockdown experiments results in semi or total lethality of the mutants, demonstrating the importance of activating them. The efficiency of these adaptive mechanisms decreases with age and leads to reduction in adult life span of the mutants. In particular, mutants develop cardiac dysfunction with age, likely reflecting the high energy requirement of a well-functioning heart. The lipases also regulate physiological triacylglycerol homeostasis and are important for energy metabolism since midgut specific reduction of them in wild type flies results in increased sensitivity to starvation and accumulation of triglycerides leading to cardiac defects. The central findings of increased AKT activation, decreased FOXO level and activation of phosphoglyceromutase and pyruvate kinase are also observed in mice heterozygous for ceramide transfer protein suggesting a conserved role of this pathway in mammals. These data reveal novel glycolytic and non-autonomous lipolytic pathways in response to increased ceramide for sustenance of high energy demanding organ functions like the heart