ARMC12 regulates spatiotemporal mitochondrial dynamics during spermiogenesis and is required for male fertility

The mammalian sperm midpiece has a unique double-helical structure called the mitochondrial sheath that wraps tightly around the axoneme. Despite the remarkable organization of the mitochondrial sheath, the molecular mechanisms involved in mitochondrial sheath formation are unclear. In the process of screening testis-enriched genes for functions in mice, we identified armadillo repeat-containing 12 (ARMC12) as an essential protein for mitochondrial sheath formation. Here, we engineered Armc12-null mice, FLAG-tagged Armc12 knock-in mice, and TBC1 domain family member 21 (Tbc1d21)-null mice to define the functions of ARMC12 in mitochondrial sheath formation in vivo. We discovered that absence of ARMC12 causes abnormal mitochondrial coiling along the flagellum, resulting in reduced sperm motility and male sterility. During spermiogenesis, sperm mitochondria in Armc12-null mice cannot elongate properly at the mitochondrial interlocking step which disrupts abnormal mitochondrial coiling. ARMC12 is a mitochondrial peripheral membrane protein and functions as an adherence factor between mitochondria in cultured cells. ARMC12 in testicular germ cells interacts with mitochondrial proteins MIC60, VDAC2, and VDAC3 as well as TBC1D21 and GK2, which are required for mitochondrial sheath formation. We also observed that TBC1D21 is essential for the interaction between ARMC12 and VDAC proteins in vivo. These results indicate that ARMC12 uses integral mitochondrial membrane proteins VDAC2 and VDAC3 as scaffolds to link mitochondria and works cooperatively with TBC1D21. Thus, our studies have revealed that ARMC12 regulates spatiotemporal mitochondrial dynamics to form the mitochondrial sheath through cooperative interactions with several proteins on the sperm mitochondrial surface.

Download Full-text

Effector caspase Dcp-1 and IAP protein Bruce regulate starvation-induced autophagy during Drosophila melanogaster oogenesis

The Journal of Cell Biology ◽

10.1083/jcb.200712091 ◽

2008 ◽

Vol 182 (6) ◽

pp. 1127-1139 ◽

Cited By ~ 108

Author(s):

Ying-Chen Claire Hou ◽

Suganthi Chittaranjan ◽

Sharon González Barbosa ◽

Kimberly McCall ◽

Sharon M. Gorski

Keyword(s):

Cell Death ◽

Drosophila Melanogaster ◽

Molecular Mechanisms ◽

Cultured Cells ◽

Mitogen Activated Protein Kinase ◽

Nuclear Condensation ◽

Effector Caspase ◽

Apoptosis Protein ◽

Egg Chambers

A complex relationship exists between autophagy and apoptosis, but the regulatory mechanisms underlying their interactions are largely unknown. We conducted a systematic study of Drosophila melanogaster cell death–related genes to determine their requirement in the regulation of starvation-induced autophagy. We discovered that six cell death genes—death caspase-1 (Dcp-1), hid, Bruce, Buffy, debcl, and p53—as well as Ras–Raf–mitogen activated protein kinase signaling pathway components had a role in autophagy regulation in D. melanogaster cultured cells. During D. melanogaster oogenesis, we found that autophagy is induced at two nutrient status checkpoints: germarium and mid-oogenesis. At these two stages, the effector caspase Dcp-1 and the inhibitor of apoptosis protein Bruce function to regulate both autophagy and starvation-induced cell death. Mutations in Atg1 and Atg7 resulted in reduced DNA fragmentation in degenerating midstage egg chambers but did not appear to affect nuclear condensation, which indicates that autophagy contributes in part to cell death in the ovary. Our study provides new insights into the molecular mechanisms that coordinately regulate autophagic and apoptotic events in vivo.

Download Full-text

Quantitative intravital imaging reveals in vivo dynamics of physiological-stress induced mitophagy

10.1101/2020.03.26.010405 ◽

2020 ◽

Author(s):

Paul J. Wrighton ◽

Arkadi Shwartz ◽

Jin-Mi Heo ◽

Eleanor D. Quenzer ◽

Kyle A. LaBella ◽

...

Keyword(s):

Molecular Mechanisms ◽

Cultured Cells ◽

Physiological Stress ◽

Hypoxia Inducible Factor ◽

Imaging Study ◽

Time Lapse ◽

Intravital Imaging ◽

Response Dynamics ◽

Pathway Activation

ABSTRACTMitophagy, the selective recycling of mitochondria through autophagy, is a crucial metabolic process induced by cellular stress, and defects are linked to aging, sarcopenia, and neurodegenerative diseases. To therapeutically target mitophagy, the fundamental in vivo dynamics and molecular mechanisms must be fully understood. Here, we generated mitophagy biosensor zebrafish lines expressing mitochondrially targeted, pH-sensitive, fluorescent probes mito-Keima and mito-EGFP-mCherry and used quantitative intravital imaging to illuminate mitophagy during physiological stresses—embryonic development, fasting and hypoxia. In fasted muscle, volumetric mitolysosome size analyses documented organelle stress-response dynamics, and time-lapse imaging revealed mitochondrial filaments undergo piecemeal fragmentation and recycling rather than the wholesale turnover observed in cultured cells. Hypoxia-inducible factor (Hif) pathway activation through physiological hypoxia or chemical or genetic modulation also provoked mitophagy. Intriguingly, mutation of a single mitophagy receptor bnip3 prevented this effect, whereas disruption of other putative hypoxia-associated mitophagy genes bnip3la (nix), fundc1, pink1 or prkn (Parkin) had no effect. This in vivo imaging study establishes fundamental dynamics of fasting-induced mitophagy and identifies bnip3 as the master regulator of Hif-induced mitophagy in vertebrate muscle.

Download Full-text

Oligodendrocyte precursor (O-2A progenitor cell) migration; a model system for the study of cell migration in the developing central nervous system

Development ◽

10.1242/dev.119.supplement.219 ◽

1993 ◽

Vol 119 (Supplement) ◽

pp. 219-225 ◽

Cited By ~ 2

Author(s):

B. W. Kiernan ◽

Charles ffrench-Constant

Keyword(s):

Nervous System ◽

Cell Migration ◽

Progenitor Cell ◽

Molecular Mechanisms ◽

Cultured Cells ◽

Large Numbers ◽

Multicellular Organisms ◽

Developing Nervous System

Cell migration plays an important role in the development of complex multicellular organisms. The molecular mechanisms that regulate this migration arc therefore of great interest. Unfortunately, however, analysis of cell migration in vertebrates is hampered by the inaccessability of the cells and the difficulty of manipulating their environment within the embryo. This review focusses on one particular migratory cell population, the oligodendrocyte p1ecursor cell or O-2A progenitor cell, that gives rise to the myelin-forming oligodendrocytes within the CNS. These cells mi grate extensively during normal development. They can be purified and grown in large numbers in cell culture, so allowing the use of reductionist approaches using cell and molecular biology techniques. Moreover, cultured cells will migrate within the CNS following transplantation. As a result, the migration of these cells in vivo can be analysed following manipulation in vitro. Taken together, we believe that the different properties of these cells makes them excellent candidates for studies addressing the control of cell migration in the developing nervous system.

Download Full-text

P0407THE INVESTIGATION OF SYNAPTOPODIN EXPRESSION OF PODOCYTES IN GLOMERONEPHRITIS

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfaa142.p0407 ◽

2020 ◽

Vol 35 (Supplement_3) ◽

Author(s):

Zhigang Zhang

Keyword(s):

Molecular Mechanisms ◽

Cultured Cells ◽

Glomerular Diseases ◽

Podocyte Injury ◽

Adriamycin Nephropathy ◽

Assembly Result ◽

And Function ◽

Rhoa Signaling ◽

New Strategies

Abstract Background and Aims Synaptopodin, a proline-rich actin-associated protein, plays an important role in the regulation of podocytes processes structures and dynamics. The mutation or lack of synaptopodin may lead to the changes of podocytes structures and functions and cause the occurrence of proteinuria. But the underlying molecular mechanisms remain primarily elusive. Method we used cellular and pathological experiments to observe the expression changes synaptopodin in vivo and vitrio. Results The results showed that the reduction expression of synaptopodin and RhoA were found in the podocytes in different nephriris of human renal biopsy as well as in rat adriamycin nephropathy. The cultured cells treated with inflammatory cytokins such as TNF, IL-1 also showed decreased synaptopodin level in podocyte, which led to low RhoA level and disarrange the actin cytoskeleton assembly, result in the abnormal changes of podocyte morphology. Conclusion These data preliminarily proved that synaptopodin loss in podocyte injury plays an important role in the regulation of podocyte morphology and function through RhoA signaling pathway, and further researches are required to clarify the more mechanism, which may provide new strategies and methods for the prevention and treatment of glomerular diseases.

Download Full-text

Androgen-receptor-interacting nuclear proteins

Biochemical Society Transactions ◽

10.1042/bst0280401 ◽

2000 ◽

Vol 28 (4) ◽

pp. 401-405 ◽

Cited By ~ 42

Author(s):

O. A. Jänne ◽

A.-M. Moilanen ◽

H. Poukka ◽

N. Rouleau ◽

U. Karvonen ◽

...

Keyword(s):

Androgen Receptor ◽

Protein Kinase ◽

Molecular Mechanisms ◽

Hormone Receptors ◽

Cultured Cells ◽

Ring Finger ◽

Interacting Protein ◽

Transcription Activators

Androgen receptor (AR) belongs to the super-family of nuclear hormone receptors that employ complex molecular mechanisms to guide the development and physiological functions of their target tissues. Our recent work has led to the identification of four novel proteins that recognize AR zinc-finger region (ZFR) both in vivo and in vitro. One is a small nuclear RING-finger protein that possesses separate interaction interfaces for AR and for other transcription activators such as Spl. The second is a nuclear serine/threonine protein kinase (androgen-receptor-interacting nuclear protein kinase; ANPK); however, the receptor itself does not seem to be a substrate for this kinase. The third one is dubbed androgen-receptor-interacting protein 3 (ARIP3) and is a novel member of the PIAS (protein inhibitor of activated STAT) protein family. The fourth protein, termed ARIP4, is a nuclear ATPase that belongs to the SNF2-like family of chromatin remodelling proteins. All four proteins exhibit a punctate nuclear pattern when expressed in cultured cells. Each protein modulates AR-dependent transactivation in co-transfection experiments; their activating functions are not restricted to AR. Current work is aimed at elucidating the biochemical and functional properties of these AR-interacting proteins and at finding the partner proteins that form complexes with them in vivo.

Download Full-text

Inhibition of the SDF-1α–CXCR4 axis by the CXCR4 antagonist AMD3100 suppresses the migration of cultured cells from ATL patients and murine lymphoblastoid cells from HTLV-I Tax transgenic mice

Blood ◽

10.1182/blood-2008-11-189308 ◽

2009 ◽

Vol 114 (14) ◽

pp. 2961-2968 ◽

Cited By ~ 43

Author(s):

Akira Kawaguchi ◽

Yasuko Orba ◽

Takashi Kimura ◽

Hidekatsu Iha ◽

Masao Ogata ◽

...

Keyword(s):

T Cell ◽

Molecular Mechanisms ◽

Cultured Cells ◽

Leukemic Cell ◽

Surface Expression ◽

Cell Infiltration ◽

Type I ◽

Cxcr4 Antagonist ◽

Adult T Cell Leukemia

Adult T-cell leukemia (ATL) is a T-cell malignancy caused by human T lymphotropic virus type I, and presents as an aggressive leukemia with characteristic widespread leukemic cell infiltration into visceral organs and skin. The molecular mechanisms associated with leukemic cell infiltration are poorly understood. We have used mouse models of ATL to investigate the role of chemokines in this process. Transfer of splenic lymphomatous cells from transgenic to SCID mice reproduces a leukemia and lymphoma that is histologically identical to human disease. It could be shown that lymphomatous cells exhibit specific chemotactic activity in response to stromal cell–derived factor-1α (SDF-1α). Lymphomatous cells exhibited surface expression of CXCR4, the specific receptor of SDF-1α. AMD3100, a CXCR4 antagonist, was found to inhibit both SDF-1α–induced migration and phosphorylation of extracellular signal-related kinase 1/2. Investigation of cultured cells from human ATL patients revealed identical findings. Using the SCID mouse model, it could be demonstrated that AMD3100 inhibited infiltration of lymphomatous cells into liver and lung tissues in vivo. These results demonstrate the involvement of the SDF-1α/CXCR4 interaction as one mechanism of leukemic cell migration and this may provide a novel target as part of combination therapy for ATL.

Download Full-text

Mechanisms, pathophysiological roles and methods for analyzing mitophagy – recent insights

Biological Chemistry ◽

10.1515/hsz-2017-0228 ◽

2018 ◽

Vol 399 (2) ◽

pp. 147-178 ◽

Cited By ~ 29

Author(s):

Jessica A. Williams ◽

Wen-Xing Ding

Keyword(s):

Molecular Mechanisms ◽

Cultured Cells ◽

Molecular Tools ◽

Mouse Tissues

Abstract In 2012, we briefly summarized the mechanisms, pathophysiological roles and methods for analyzing mitophagy. As then, the mitophagy field has continued to grow rapidly, and many new molecular mechanisms regulating mitophagy and molecular tools for monitoring mitophagy have been discovered and developed. Therefore, the purpose of this review is to update information regarding these advances in mitophagy while focusing on basic molecular mechanisms of mitophagy in different organisms and its pathophysiological roles. We also discuss the advantage and limitations of current methods to monitor and quantify mitophagy in cultured cells and in vivo mouse tissues.

Download Full-text

Somatic Mutation Theory - Why it's Wrong for Most Cancers

Cellular Physiology and Biochemistry ◽

10.1159/000443106 ◽

2016 ◽

Vol 38 (5) ◽

pp. 1663-1680 ◽

Cited By ~ 29

Author(s):

Björn L.D.M. Brücher ◽

Ijaz S. Jamall

Keyword(s):

Somatic Mutation ◽

Somatic Mutations ◽

Chemical Carcinogenesis ◽

Helical Structure ◽

Somatic Mutation Theory ◽

Double Helical Structure ◽

Mutation Theory ◽

Risk Of Cancer

Hysteron proteron reverses both temporal and logical order and this syllogism occurs in carcinogenesis and the somatic mutation theory (SMT): the first (somatic mutation) occurs only after the second (onset of cancer) and, therefore, observed somatic mutations in most cancers appear well after the early cues of carcinogenesis are in place. It is no accident that mutations are increasingly being questioned as the causal event in the origin of the vast majority of cancers as clinical data show little support for this theory when compared against the metrics of patient outcomes. Ever since the discovery of the double helical structure of DNA, virtually all chronic diseases came to be viewed as causally linked to one degree or another to mutations, even though we now know that genes are not simply blueprints, but rather an assemblage of alphabets that can, under non-genetic influences, be used to assemble a business letter or a work of Shakespearean literature. A minority of all cancers is indeed caused by mutations but the SMT has been applied to all cancers, and even to chemical carcinogenesis, in the absence of hard evidence of causality. Herein, we review the 100 year story of SMT and aspects that show why genes are not just blueprints, how radiation and mutation are associated in a more nuanced view, the proposed risk of cancer and bad luck, and the in vitro and in vivo evidence for a new cancer paradigm. This paradigm is scientifically applicable for the majority of non-heritable cancers and consists of a six-step sequence for the origin of cancer. This new cancer paradigm proclaims that somatic mutations are epiphenomena or later events occurring after carcinogenesis is already underway. This serves not just as a plausible alternative to SMT and explains the origin of the majority of cancers, but also provides opportunities for early interventions and prevention of the onset of cancer as a disease.

Download Full-text

Structural recognition of the mRNA 3′ UTR by PUF-8 restricts the lifespan of C. elegans

Nucleic Acids Research ◽

10.1093/nar/gkab754 ◽

2021 ◽

Author(s):

Zheng Xu ◽

Jie Zhao ◽

Minjie Hong ◽

Chenming Zeng ◽

Shouhong Guang ◽

...

Keyword(s):

Molecular Mechanisms ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Model Organism ◽

Untranslated Regions ◽

Germline Development ◽

C Elegans ◽

Target Mrnas ◽

Puf Domain

Abstract The molecular mechanisms of aging are unsolved fundamental biological questions. Caenorhabditis elegans is an ideal model organism for investigating aging. PUF-8, a PUF (Pumilio and FBF) protein in C. elegans, is crucial for germline development through binding with the 3′ untranslated regions (3′ UTR) in the target mRNAs. Recently, PUF-8 was reported to alter mitochondrial dynamics and mitophagy by regulating MFF-1, a mitochondrial fission factor, and subsequently regulated longevity. Here, we determined the crystal structure of the PUF domain of PUF-8 with an RNA substrate. Mutagenesis experiments were performed to alter PUF-8 recognition of its target mRNAs. Those mutations reduced the fertility and extended the lifespan of C. elegans. Deep sequencing of total mRNAs from wild-type and puf-8 mutant worms as well as in vivo RNA Crosslinking and Immunoprecipitation (CLIP) experiments identified six PUF-8 regulated genes, which contain at least one PUF-binding element (PBE) at the 3′ UTR. One of the six genes, pqm-1, is crucial for lipid storage and aging process. Knockdown of pqm-1 could revert the lifespan extension of puf-8 mutant animals. We conclude that PUF-8 regulate the lifespan of C. elegans may not only via MFF but also via modulating pqm-1-related pathways.

Download Full-text

Abstract 283: SGK1-Dependent Sirt3 Phosphorylation Regulates Mitochondrial Dynamics

Circulation Research ◽

10.1161/res.119.suppl_1.283 ◽

2016 ◽

Vol 119 (suppl_1) ◽

Author(s):

Dallas Ellis ◽

Takara Scott ◽

Wei Zhong ◽

Oguljahan Babayeva ◽

Sharon C Francis

Keyword(s):

Molecular Mechanisms ◽

Mitochondrial Dynamics ◽

Mitochondrial Fission ◽

Ectopic Expression ◽

Mitochondrial Fragmentation ◽

Proteomic Screen ◽

Protein Levels ◽

Stimulation Of

Mitochondrial dynamics (i.e. fusion and fission) is impaired in models of obesity and can result in target organ dysfunction. However, the mechanisms that regulate mitochondrial dynamics in the setting of obesity are not completely understood. The objectives of this study are to examine a role for and determine the molecular mechanisms of serum and glucocorticoid-inducible kinase 1 (SGK1) in obesity-related mitochondrial dynamics in the vasculature. We recently reported that aortic expression of SGK1 is elevated in a model of diet-induced obesity (DIO) in vivo and by resistin; a fat-derived adipokine, in human aortic smooth muscle cells (SMC) in vitro . To directly examine the effects of SMC-derived SGK1 on mitochondrial dynamics, wildtype and SMC-specific SGK1 knockout mice were subjected to DIO for eight weeks. Our results indicate that SMC-specific deletion of SGK1 induced a fused, elongated mitochondrial phenotype in aortic SMC in vivo and attenuated obesity-mediated arterial mitochondrial fragmentation suggesting a role for SGK1 in stimulation of mitochondrial fission. To determine the molecular mechanism for this effect, we performed a proteomic screen for novel SGK1 substrates and identified the mitochondrial deacetylase SIRT3 as a novel SGK1 target. Mass spectrometry indicates SGK1 phosphorylates SIRT3 on serine103. Increasing doses of resistin augmented SIRT3-S103 phosphorylation and caused a concomitant decrease in total SIRT3 in rat aortic SMC in vitro . To examine whether SGK1-dependent SIRT3 phosphorylation regulates the mitochondrial fission protein machinery; we evaluated total and activated levels of Drp1, the mitochondrial fission regulator, in response to ectopic expression of SIRT3 wildtype, phospho-memetic (S103D) and phospho-deficient (S103A) mutants. SIRT3-S103D increased total Drp1 and activated Drp1 protein levels an effect inhibited by SIRT3-S103A. These findings implicate elevated resistin observed during obesity in stimulation of SGK1 and subsequent phosphorylation of SIRT3 leading to activation of Drp1 and stimulation of arterial mitochondrial fragmentation.

Download Full-text