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Guseva EA, Buev VS, Mirzaeva SE, Pletnev PI, Dontsova OA, Sergiev PV. Structure and Composition of Spermatozoa Fibrous Sheath in Diverse Groups of Metazoa. Int J Mol Sci 2024; 25:7663. [PMID: 39062905 PMCID: PMC11276731 DOI: 10.3390/ijms25147663] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 07/01/2024] [Accepted: 07/08/2024] [Indexed: 07/28/2024] Open
Abstract
The proper functioning and assembly of the sperm flagella structures contribute significantly to spermatozoa motility and overall male fertility. However, the fine mechanisms of assembly steps are poorly studied due to the high diversity of cell types, low solubility of the corresponding protein structures, and high tissue and cell specificity. One of the open questions for investigation is the attachment of longitudinal columns to the doublets 3 and 8 of axonemal microtubules through the outer dense fibers. A number of mutations affecting the assembly of flagella in model organisms are known. Additionally, evolutionary genomics data and comparative analysis of flagella morphology are available for a set of non-model species. This review is devoted to the analysis of diverse ultrastructures of sperm flagellum of Metazoa combined with an overview of the evolutionary distribution and function of the mammalian fibrous sheath proteins.
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Affiliation(s)
- Ekaterina A. Guseva
- Center of Life Sciences, Skolkovo Institute of Science and Technology, 143025 Skolkovo, Russia; (E.A.G.); (O.A.D.)
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
- Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; (V.S.B.); (S.E.M.); (P.I.P.)
| | - Vitaly S. Buev
- Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; (V.S.B.); (S.E.M.); (P.I.P.)
- Faculty of Bioengeneering and Bioinformatics, Lomonosov Moscow State University, 119991 Moscow, Russia
| | - Sabina E. Mirzaeva
- Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; (V.S.B.); (S.E.M.); (P.I.P.)
| | - Philipp I. Pletnev
- Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; (V.S.B.); (S.E.M.); (P.I.P.)
| | - Olga A. Dontsova
- Center of Life Sciences, Skolkovo Institute of Science and Technology, 143025 Skolkovo, Russia; (E.A.G.); (O.A.D.)
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
- Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; (V.S.B.); (S.E.M.); (P.I.P.)
- Shemyakin–Ovchinnikov Institute of Bioorganic Chemistry, 117997 Moscow, Russia
| | - Petr V. Sergiev
- Center of Life Sciences, Skolkovo Institute of Science and Technology, 143025 Skolkovo, Russia; (E.A.G.); (O.A.D.)
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, 119991 Moscow, Russia
- Faculty of Chemistry, Lomonosov Moscow State University, 119991 Moscow, Russia; (V.S.B.); (S.E.M.); (P.I.P.)
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Yamamoto C, Takahashi F, Suetsugu N, Yamada K, Yoshikawa S, Kohchi T, Kasahara M. The cAMP signaling module regulates sperm motility in the liverwort Marchantia polymorpha. Proc Natl Acad Sci U S A 2024; 121:e2322211121. [PMID: 38593080 PMCID: PMC11032487 DOI: 10.1073/pnas.2322211121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 03/14/2024] [Indexed: 04/11/2024] Open
Abstract
Adenosine 3',5'-cyclic monophosphate (cAMP) is a universal signaling molecule that acts as a second messenger in various organisms. It is well established that cAMP plays essential roles across the tree of life, although the function of cAMP in land plants has long been debated. We previously identified the enzyme with both adenylyl cyclase (AC) and cAMP phosphodiesterase (PDE) activity as the cAMP-synthesis/hydrolysis enzyme COMBINED AC with PDE (CAPE) in the liverwort Marchantia polymorpha. CAPE is conserved in streptophytes that reproduce with motile sperm; however, the precise function of CAPE is not yet known. In this study, we demonstrate that the loss of function of CAPE in M. polymorpha led to male infertility due to impaired sperm flagellar motility. We also found that two genes encoding the regulatory subunits of cAMP-dependent protein kinase (PKA-R) were also involved in sperm motility. Based on these findings, it is evident that CAPE and PKA-Rs act as a cAMP signaling module that regulates sperm motility in M. polymorpha. Therefore, our results have shed light on the function of cAMP signaling and sperm motility regulators in land plants. This study suggests that cAMP signaling plays a common role in plant and animal sperm motility.
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Affiliation(s)
- Chiaki Yamamoto
- Department of Biotechnology, Graduate School of Life Sciences, Ritsumeikan University, Kusatsu525-8577, Japan
| | - Fumio Takahashi
- Department of Biotechnology, Graduate School of Life Sciences, Ritsumeikan University, Kusatsu525-8577, Japan
| | - Noriyuki Suetsugu
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo153-8902, Japan
| | - Kazumasa Yamada
- Department of Marine Science and Technology, Faculty of Marine Science and Technology, Fukui Prefectural University, Obama917-0003, Japan
| | - Shinya Yoshikawa
- Department of Marine Science and Technology, Faculty of Marine Science and Technology, Fukui Prefectural University, Obama917-0003, Japan
| | - Takayuki Kohchi
- Division of Integrated Life Science, Graduate School of Biostudies, Kyoto University, Kyoto606-8502, Japan
| | - Masahiro Kasahara
- Department of Biotechnology, Graduate School of Life Sciences, Ritsumeikan University, Kusatsu525-8577, Japan
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3
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Campolo F, Assenza MR, Venneri MA, Barbagallo F. Once upon a Testis: The Tale of Cyclic Nucleotide Phosphodiesterase in Testicular Cancers. Int J Mol Sci 2023; 24:ijms24087617. [PMID: 37108780 PMCID: PMC10146088 DOI: 10.3390/ijms24087617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 04/17/2023] [Accepted: 04/19/2023] [Indexed: 04/29/2023] Open
Abstract
Phosphodiesterases are key regulators that fine tune the intracellular levels of cyclic nucleotides, given their ability to hydrolyze cAMP and cGMP. They are critical regulators of cAMP/cGMP-mediated signaling pathways, modulating their downstream biological effects such as gene expression, cell proliferation, cell-cycle regulation but also inflammation and metabolic function. Recently, mutations in PDE genes have been identified and linked to human genetic diseases and PDEs have been demonstrated to play a potential role in predisposition to several tumors, especially in cAMP-sensitive tissues. This review summarizes the current knowledge and most relevant findings regarding the expression and regulation of PDE families in the testis focusing on PDEs role in testicular cancer development.
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Affiliation(s)
- Federica Campolo
- Department of Experimental Medicine, Sapienza University of Rome, 00161 Rome, Italy
| | - Maria Rita Assenza
- Faculty of Medicine and Surgery, "Kore" University of Enna, 94100 Enna, Italy
| | - Mary Anna Venneri
- Department of Experimental Medicine, Sapienza University of Rome, 00161 Rome, Italy
| | - Federica Barbagallo
- Faculty of Medicine and Surgery, "Kore" University of Enna, 94100 Enna, Italy
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4
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Campolo F, Capponi C, Tarsitano MG, Tenuta M, Pozza C, Gianfrilli D, Magliocca F, Venneri MA, Vicini E, Lenzi A, Isidori AM, Barbagallo F. cAMP-specific phosphodiesterase 8A and 8B isoforms are differentially expressed in human testis and Leydig cell tumor. Front Endocrinol (Lausanne) 2022; 13:1010924. [PMID: 36277728 PMCID: PMC9585345 DOI: 10.3389/fendo.2022.1010924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2022] [Accepted: 09/06/2022] [Indexed: 11/21/2022] Open
Abstract
Cyclic adenosine monophosphate/Protein kinase A (cAMP/PKA) signaling pathway is the master regulator of endocrine tissue function. The level, compartmentalization and amplitude of cAMP response are finely regulated by phosphodiesterases (PDEs). PDE8 is responsible of cAMP hydrolysis and its expression has been characterized in all steroidogenic cell types in rodents including adrenal and Leydig cells in rodents however scarce data are currently available in humans. Here we demonstrate that human Leydig cells express both PDE8A and PDE8B isoforms. Interestingly, we found that the expression of PDE8B but not of PDE8A is increased in transformed Leydig cells (Leydig cell tumors-LCTs) compared to non-tumoral cells. Immunofluorescence analyses further reveals that PDE8A is also highly expressed in specific spermatogenic stages. While the protein is not detected in spermatogonia it accumulates nearby the forming acrosome, in the trans-Golgi apparatus of spermatocytes and spermatids and it follows the fate of this organelle in the later stages translocating to the caudal part of the cell. Taken together our findings suggest that 1) a specific pool(s) of cAMP is/are regulated by PDE8A during spermiogenesis pointing out a possible new role of this PDE8 isoform in key events governing the differentiation and maturation of human sperm and 2) PDE8B can be involved in Leydig cell transformation.
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Affiliation(s)
- Federica Campolo
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Chiara Capponi
- Department of Anatomical, Histological, Forensic and Orthopedic Sciences, Sapienza University of Rome, Rome, Italy
| | - Maria Grazia Tarsitano
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
- Department of Medical and Surgical Sciences, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Marta Tenuta
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Carlotta Pozza
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Daniele Gianfrilli
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Fabio Magliocca
- Department of Radiological, Oncological and Pathological Sciences, Sapienza University of Rome, Rome, Italy
| | - Mary A. Venneri
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Elena Vicini
- Department of Anatomical, Histological, Forensic and Orthopedic Sciences, Sapienza University of Rome, Rome, Italy
| | - Andrea Lenzi
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Andrea M. Isidori
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
| | - Federica Barbagallo
- Department of Experimental Medicine, Sapienza University of Rome, Rome, Italy
- Faculty of Medicine and Surgery, Kore University of Enna, Enna, Italy
- *Correspondence: Federica Barbagallo,
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Yeast Two-Hybrid Screen Identifies PKA-Riα Interacting Proteins during Mouse Spermiogenesis. Genes (Basel) 2021; 12:genes12121941. [PMID: 34946890 PMCID: PMC8700991 DOI: 10.3390/genes12121941] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 11/26/2021] [Accepted: 11/29/2021] [Indexed: 12/26/2022] Open
Abstract
cAMP-dependent protein kinase (PKA) signaling plays various roles during mammalian spermatogenesis, ranging from the regulation of gene expression to the modulation of sperm motility. However, the molecular mechanisms that govern the multifaceted functions of PKA during spermatogenesis remain largely unclear. We previously found that PKA regulatory subunit I α (RIα) and catalytic subunit α (Cα) co-sediment with polyribosomal fractions of mouse testis lysate on sucrose gradient and the stimulation of PKA activity facilitates protein synthesis in post-meiotic elongating spermatids, indicating that type I PKA is intricately associated with protein translation machinery and regulates protein synthesis during mouse spermiogenesis. Since PKA activity is often regulated by interacting proteins that form complexes with its regulatory subunits, the identification of PKA-RIα interacting proteins in post-meiotic spermatogenic cells will facilitate our understanding of its regulatory roles in protein synthesis and spermiogenesis. In the present study, we applied a yeast two-hybrid screen to identify PKA-Riα-binding proteins using a cDNA library generated from mouse round and elongating spermatids. Numerous proteins were found to potentially interact with PKA-RIα, including proteostasis modulators, metabolic enzymes, cytoskeletal regulators, and mitochondrial proteins, many of which are specifically expressed in testes. Consistently, the examination of MENA (mouse ENA/VASP homolog) in developing mouse testes suggested that post-meiotic spermatogenic cells express a short isoform of MENA that interacts with PKA-RIα in yeast two-hybrid assay. The identification of PKA-RIα interacting proteins provides us solid basis to further explore how PKA signaling regulates protein synthesis and cellular morphogenesis during mouse spermatogenesis.
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Baro Graf C, Ritagliati C, Stival C, Luque GM, Gentile I, Buffone MG, Krapf D. Everything you ever wanted to know about PKA regulation and its involvement in mammalian sperm capacitation. Mol Cell Endocrinol 2020; 518:110992. [PMID: 32853743 DOI: 10.1016/j.mce.2020.110992] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Revised: 08/11/2020] [Accepted: 08/12/2020] [Indexed: 12/29/2022]
Abstract
The 3', 5'-cyclic adenosine monophosphate (cAMP) dependent protein kinase (PKA) is a tetrameric holoenzyme comprising a set of two regulatory subunits (PKA-R) and two catalytic (PKA-C) subunits. The PKA-R subunits act as sensors of cAMP and allow PKA-C activity. One of the first signaling events observed during mammalian sperm capacitation is PKA activation. Thus, understanding how PKA activity is restricted in space and time is crucial to decipher the critical steps of sperm capacitation. It is widely accepted that PKA specificity depends on several levels of regulation. Anchoring proteins play a pivotal role in achieving proper localization signaling, subcellular targeting and cAMP microdomains. These multi-factorial regulation steps are necessary for a precise spatio-temporal activation of PKA. Here we discuss recent understanding of regulatory mechanisms of PKA in mammalian sperm, such as post-translational modifications, in the context of its role as the master orchestrator of molecular events conducive to capacitation.
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Affiliation(s)
- Carolina Baro Graf
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET-UNR, Rosario, Argentina; Laboratorio de Medicina Reproductiva (LMR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina
| | - Carla Ritagliati
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET-UNR, Rosario, Argentina
| | - Cintia Stival
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET-UNR, Rosario, Argentina
| | - Guillermina M Luque
- Laboratory of Cellular and Molecular Reproductive Biology, Instituto de Biología y Medicina Experimental (IBYME), CONICET, Buenos Aires, Argentina
| | - Iñaki Gentile
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET-UNR, Rosario, Argentina
| | - Mariano G Buffone
- Laboratory of Cellular and Molecular Reproductive Biology, Instituto de Biología y Medicina Experimental (IBYME), CONICET, Buenos Aires, Argentina
| | - Dario Krapf
- Laboratory of Cell Signal Transduction Networks, Instituto de Biología Molecular y Celular de Rosario (IBR), CONICET-UNR, Rosario, Argentina; Laboratorio de Medicina Reproductiva (LMR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
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7
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cAMP-PKA signal transduction specificity in Saccharomyces cerevisiae. Curr Genet 2020; 66:1093-1099. [PMID: 32935175 DOI: 10.1007/s00294-020-01107-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2020] [Revised: 08/23/2020] [Accepted: 09/01/2020] [Indexed: 01/02/2023]
Abstract
Living cells have developed a set of complex signaling responses, which allow them to withstand different environmental challenges. Signaling pathways enable the cell to monitor external and internal states and to articulate the appropriate physiological responses. Cellular signal transmission requires the dynamic formation of spatiotemporal controlled molecular interactions. One of the most important signaling circuits in Saccharomyces cerevisiae is the one controlled by cAMP-Protein Kinase A (PKA). In budding yeast, extracellular glucose and a plethora of signals related with growth and stress conditions regulate the intracellular cAMP levels that modulate PKA activity which in turn regulates a broad range of cellular processes. The cAMP-PKA signaling output requires a controlled specificity of the PKA responses. In this review we discuss the molecular mechanisms that are involved in the establishment of the specificity in the cAMP-PKA signaling pathway in S.cerevisiae.
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8
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Martin LJ, Roumaud P. Modulation of the transcriptomic profile of the R2C tumor Leydig cell line by the adipose tissue derived hormone leptin. Reprod Biol 2018; 18:440-449. [PMID: 30174195 DOI: 10.1016/j.repbio.2018.08.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Revised: 08/17/2018] [Accepted: 08/25/2018] [Indexed: 12/14/2022]
Abstract
Leptin is an important adipose derived hormone being secreted by adipocytes and involved in appetite regulation. Disruption of normal plasma levels of leptin has been associated with the pathogenesis of obesity. It is now well established that obesity is associated to an increased risk of cancer development, including testicular cancers. Recently, we have shown that high levels of leptin have inhibitory effects on cAMP-dependent steroidogenic genes expression in MA-10 Leydig cells. Hence, we examined if leptin could alter the transcriptome of the constitutively steroidogenic rat tumor Leydig cell line R2C. These cells were treated with high levels of leptin (1000 ng/ml) for 4 h, followed by mRNA extraction and RNA-Seq analysis. Interestingly, leptin had no effect on steroidogenic gene expression or pathways promoting tumorigenesis of this cell line. Genes being upregulated or downregulated by leptin were enriched in biological processes that were non-relevant to Leydig cell function. Surprisingly, lepr isoforms were weakly expressed in R2C cells and may explain in part the low levels of leptin's response for tumor Leydig cells. Hence, the current findings suggest that acute treatments of tumor Leydig cells with high levels of leptin have negligible effects on transcriptomics and rather supports that leptin would have a central effect on the hypothalamus to influence testicular function.
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Affiliation(s)
- Luc J Martin
- Biology Department, Université de Moncton, Moncton, New-Brunswick, E1A 3E9 Canada.
| | - Pauline Roumaud
- Biology Department, Université de Moncton, Moncton, New-Brunswick, E1A 3E9 Canada
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9
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Balbach M, Beckert V, Hansen JN, Wachten D. Shedding light on the role of cAMP in mammalian sperm physiology. Mol Cell Endocrinol 2018; 468:111-120. [PMID: 29146556 DOI: 10.1016/j.mce.2017.11.008] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 11/10/2017] [Accepted: 11/10/2017] [Indexed: 12/24/2022]
Abstract
Mammalian fertilization relies on sperm finding the egg and penetrating the egg vestments. All steps in a sperm's lifetime crucially rely on changes in the second messenger cAMP (cyclic adenosine monophosphate). In recent years, it has become clear that signal transduction in sperm is not a continuum, but rather organized in subcellular domains, e.g. the sperm head and the sperm flagellum, with the latter being further separated into the midpiece, principal piece, and endpiece. To understand the underlying signaling pathways controlling sperm function in more detail, experimental approaches are needed that allow to study sperm signaling with spatial and temporal precision. Here, we will give a comprehensive overview on cAMP signaling in mammalian sperm, describing the molecular players involved in these pathways and the sperm functions that are controlled by cAMP. Furthermore, we will highlight recent advances in analyzing and manipulating sperm signaling with spatio-temporal precision using light.
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Affiliation(s)
- Melanie Balbach
- Center of Advanced European Studies and Research (caesar), Department of Molecular Sensory Systems, Bonn, Germany
| | - Vera Beckert
- Institute of Innate Immunity, University Hospital, University of Bonn, Bonn, Germany
| | - Jan N Hansen
- Institute of Innate Immunity, University Hospital, University of Bonn, Bonn, Germany
| | - Dagmar Wachten
- Institute of Innate Immunity, University Hospital, University of Bonn, Bonn, Germany; Center of Advanced European Studies and Research (caesar), Minerva Max Planck Research Group, Molecular Physiology, Bonn, Germany.
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10
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Pautasso C, Reca S, Chatfield-Reed K, Chua G, Galello F, Portela P, Zaremberg V, Rossi S. Identification of novel transcriptional regulators of PKA subunits inSaccharomyces cerevisiaeby quantitative promoter–reporter screening. FEMS Yeast Res 2016; 16:fow046. [DOI: 10.1093/femsyr/fow046] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/03/2016] [Indexed: 01/22/2023] Open
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Xu K, Qi H. Sperm-specific AKAP3 is a dual-specificity anchoring protein that interacts with both protein kinase a regulatory subunits via conserved N-terminal amphipathic peptides. Mol Reprod Dev 2014; 81:595-607. [PMID: 24687590 DOI: 10.1002/mrd.22329] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 03/22/2014] [Indexed: 11/06/2022]
Abstract
cAMP-dependent protein kinase A (PKA) plays important regulatory roles during mouse spermatogenesis. PKA-mediated signaling has been shown to regulate gene expression, chromatin condensation, capacitation, and motility during sperm development and behavior, although how PKA is regulated in spatiotemporal manners during spermatogenesis is not fully understood. In the present study, we found that PKA subunit isoforms are expressed and localized differently in meiotic and post-meiotic mouse spermatogenic cells. Regulatory subunit I alpha (RIα) is expressed in spermatocytes and round spermatids, where it is localized diffusely throughout the cytoplasm of cells. During late spermiogenesis, RIα abundance gradually decreases. On the other hand, RIIα is expressed constantly throughout meiotic and post-meiotic stages, and is associated with cytoskeletal structures. Among several A kinase anchoring proteins (AKAPs) expressed in the testis, sperm-specific AKAP3 can be found in the cytoplasm of elongating spermatids and interacts with RIα, as demonstrated by both in vivo and in vitro experiments. In mature sperm, AKAP3 is exclusively found in the principal piece of the flagellum, coincident with only RIIα. Mutagenesis experiments further showed that the preferential interactions of AKAP3 with PKA regulatory subunits are mediated by two highly conserved amphipathic peptides located in the N-terminal region of AKAP3. Thus, AKAP3 is a dual-specificity molecule that modulates PKA isotypes in a spatiotemporal manner during mouse spermatogenesis.
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Affiliation(s)
- Kaibiao Xu
- Key Laboratory of Regenerative Biology, Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, South China Institute for Stem Cell Biology and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou, China
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12
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Pautasso C, Rossi S. Transcriptional regulation of the protein kinase A subunits in Saccharomyces cerevisiae: Autoregulatory role of the kinase A activity. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2014; 1839:275-87. [DOI: 10.1016/j.bbagrm.2014.02.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Revised: 02/06/2014] [Accepted: 02/07/2014] [Indexed: 11/27/2022]
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13
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Yue X, Huan P, Xiao G, Liu B. Expression patterns of an i-type lysozyme in the clam Meretrix meretrix along with larval development. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2013; 41:27-32. [PMID: 23583308 DOI: 10.1016/j.dci.2013.04.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2012] [Revised: 04/03/2013] [Accepted: 04/03/2013] [Indexed: 06/02/2023]
Abstract
An i-type lysozyme (MmeLys) has been proved to function in immunity of the clam Meretrix meretrix in our previous studies. In this study, the expression patterns of MmeLys mRNA and protein at four chief developmental stages of M. meretrix were analyzed, which was able to provide information about how ontogeny of immunity and, in particular, antibacterial ability occured in the bivalve. The results of real-time PCR and western blot showed that MmeLys expressions were activated in D-veligers and dramatically increased to the highest level in pediveligers. It is proposed that the expression changes at these two stages might be due to the visceral organs changes, which were related to the archenteron formation in D-veligers and the organ-restructuring in pediveligers during metamorphosis. In addition, new methods of whole mount in situ hybridization and whole mount immunofluorescence were applied to identify the MmeLys expression tissues, and these tissues (i.e. hepatopancreas, gill, mantle, mouth, velum and foot) may be involved in the immune function during development of clams. Our study is valuable to a certain extent for exploring the origin of immune functions in clams and provides new methodology for future studies on the immune ontogeny of bivalves.
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Affiliation(s)
- Xin Yue
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, 7 Nanhai Road, Qingdao 266071, China
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14
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Vetter MM, Zenn HM, Méndez E, van den Boom H, Herberg FW, Skålhegg BS. The testis-specific Cα2 subunit of PKA is kinetically indistinguishable from the common Cα1 subunit of PKA. BMC BIOCHEMISTRY 2011; 12:40. [PMID: 21812984 PMCID: PMC3163529 DOI: 10.1186/1471-2091-12-40] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/02/2011] [Accepted: 08/03/2011] [Indexed: 11/22/2022]
Abstract
Background The two variants of the α-form of the catalytic (C) subunit of protein kinase A (PKA), designated Cα1 and Cα2, are encoded by the PRKACA gene. Whereas Cα1 is ubiquitous, Cα2 expression is restricted to the sperm cell. Cα1 and Cα2 are encoded with different N-terminal domains. In Cα1 but not Cα2 the N-terminal end introduces three sites for posttranslational modifications which include myristylation at Gly1, Asp-specific deamidation at Asn2 and autophosphorylation at Ser10. Previous reports have implicated specific biological features correlating with these modifications on Cα1. Since Cα2 is not modified in the same way as Cα1 we tested if they have distinct biochemical activities that may be reflected in different biological properties. Results We show that Cα2 interacts with the two major forms of the regulatory subunit (R) of PKA, RI and RII, to form cAMP-sensitive PKAI and PKAII holoenzymes both in vitro and in vivo as is also the case with Cα1. Moreover, using Surface Plasmon Resonance (SPR), we show that the interaction patterns of the physiological inhibitors RI, RII and PKI were comparable for Cα2 and Cα1. This is also the case for their potency to inhibit catalytic activities of Cα2 and Cα1. Conclusion We conclude that the regulatory complexes formed with either Cα1 or Cα2, respectively, are indistinguishable.
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Affiliation(s)
- Maike M Vetter
- Department of Nutrition, Institute of Basic Medical Sciences, University of Oslo, Pb 1046 Blindern, Oslo, Norway
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Hermo L, Pelletier RM, Cyr DG, Smith CE. Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 3: developmental changes in spermatid flagellum and cytoplasmic droplet and interaction of sperm with the zona pellucida and egg plasma membrane. Microsc Res Tech 2010; 73:320-63. [PMID: 19941287 DOI: 10.1002/jemt.20784] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Spermiogenesis constitutes the steps involved in the metamorphosis of spermatids into spermatozoa. It involves modification of several organelles in addition to the formation of several structures including the flagellum and cytoplasmic droplet. The flagellum is composed of a neck region and middle, principal, and end pieces. The axoneme composed of nine outer microtubular doublets circularly arranged to form a cylinder around a central pair of microtubules is present throughout the flagellum. The middle and principal pieces each contain specific components such as the mitochondrial sheath and fibrous sheath, respectively, while outer dense fibers are common to both. A plethora of proteins are constituents of each of these structures, with each playing key roles in functions related to the fertility of spermatozoa. At the end of spermiogenesis, a portion of spermatid cytoplasm remains associated with the released spermatozoa, referred to as the cytoplasmic droplet. The latter has as its main feature Golgi saccules, which appear to modify the plasma membrane of spermatozoa as they move down the epididymal duct and hence may be partly involved in male gamete maturation. The end product of spermatogenesis is highly streamlined and motile spermatozoa having a condensed nucleus equipped with an acrosome. Spermatozoa move through the female reproductive tract and eventually penetrate the zona pellucida and bind to the egg plasma membrane. Many proteins have been implicated in the process of fertilization as well as a plethora of proteins involved in the development of spermatids and sperm, and these are high lighted in this review.
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Affiliation(s)
- Louis Hermo
- Department of Anatomy and Cell Biology, Faculty of Medicine, McGill University, Montreal, Quebec, Canada H3A 2B2.
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16
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Dwivedi Y, Pandey GN. Adenylyl cyclase-cyclicAMP signaling in mood disorders: role of the crucial phosphorylating enzyme protein kinase A. Neuropsychiatr Dis Treat 2008; 4:161-76. [PMID: 18728821 PMCID: PMC2515915 DOI: 10.2147/ndt.s2380] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Mood disorders are among the most prevalent and recurrent forms of psychiatric illnesses. In the last decade, there has been increased understanding of the biological basis of mood disorders. In fact, novel mechanistic concepts of the neurobiology of unipolar and bipolar disorders are evolving based on recent pre-clinical and clinical studies, most of which now focus on the role of signal transduction mechanisms in these psychiatric illnesses. Particular investigative emphasis has been given to the role of phosphorylating enzymes, which are crucial in regulating gene expression and neuronal and synaptic plasticity. Among the most important phosphorylating enzyme is protein kinase A (PKA), a component of adenylyl cyclase-cyclic adenosine monophosphate (AC-cAMP) signaling system. In this review, we critically and comprehensively discuss the role of various components of AC-cAMP signaling in mood disorders, with a special focus on PKA, because of the interesting observation that have been made about its involvement in unipolar and bipolar disorders. We also discuss the functional significance of the findings regarding PKA by discussing the role of important PKA substrates, namely, Rap-1, cyclicAMP-response element binding protein, and brain-derived neurotrophic factor. These studies suggest the interesting possibility that PKA and related signaling molecules may serve as important neurobiological factors in mood disorders and may be relevant in target-specific therapeutic interventions for these disorders.
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Affiliation(s)
- Yogesh Dwivedi
- Psychiatric Institute, Department of Psychiatry, College of Medicine, University of Illinois at Chicago Chicago, Illinois 60612, USA.
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17
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Disruption of the RIIbeta subunit of PKA reverses the obesity syndrome of Agouti lethal yellow mice. Proc Natl Acad Sci U S A 2008; 105:276-81. [PMID: 18172198 DOI: 10.1073/pnas.0710607105] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Agouti lethal yellow (A(y)) mice express agouti ectopically because of a genetic rearrangement at the agouti locus. The agouti peptide is a potent antagonist of the melanocortin 4 receptor (MC4R) expressed in neurons, and this leads to hyperphagia, hypoactivity, and increased fat mass. The MC4R signals through Gs and is thought to stimulate the production of cAMP and activation of downstream cAMP effector molecules such as PKA. Disruption of the RIIbeta regulatory subunit gene of PKA results in release of the active catalytic subunit and an increase in basal PKA activity in cells where RIIbeta is highly expressed. Because RIIbeta is expressed in neurons including those in the hypothalamic nuclei where MC4R is prominent we tested the possibility that the RIIbeta knockout might rescue the body weight phenotypes of the A(y) mice. Disruption of the RIIbeta PKA regulatory subunit gene in mice leads to a 50% reduction in white adipose tissue and resistance to diet-induced obesity and hyperglycemia. The RIIbeta mutation rescued the elevated body weight, hyperphagia, and obesity of A(y) mice. Partial rescue of the A(y) phenotypes was even observed on an RIIbeta heterozygote background. These results suggest that the RIIbeta gene mutation alters adiposity and locomotor activity by modifying PKA signaling pathways downstream of the agouti antagonism of MC4R in the hypothalamus.
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18
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Abstract
Temporal and spatial regulation of PKA activity are essential for vigorous sperm motility and for the resumption of meiosis in oocytes, two events required for successful fertilization. Genetic mutations in mice that affect PKA signaling in germ cells lead to infertility and illustrate the importance of this pathway in mammalian reproduction.
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Affiliation(s)
- Kimberly A Burton
- Department of Pharmacology, University of Washington, Seattle, WA, USA
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19
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Rawe VY, Ramalho-Santos J, Payne C, Chemes HE, Schatten G. WAVE1, an A-kinase anchoring protein, during mammalian spermatogenesis. Hum Reprod 2004; 19:2594-604. [PMID: 15471936 DOI: 10.1093/humrep/deh513] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Proper compartmentalization of signalling cascades is paramount to many intracellular activities during spermatogenesis and sperm function. In the present study we focus on the A-kinase-anchoring protein (AKAP) WAVE1, a member of the Wiskott-Aldrich syndrome (WASP) family of adaptor proteins, to study its localization throughout mammalian spermatogenesis. METHODS Using transmission electron microscopy, immunocytochemistry and western blotting, we examined the distribution of WAVE1 and putative partners during mammalian spermatogenesis. The localization and association of PKA RII, the regulatory subunit II of protein kinase A, tyrosine kinase Abl, and small GTPase RAC1 were also explored. RESULTS WAVE1 localization in spermatocytes and round spermatids coincided with Golgi apparatus distribution, whereas in elongated spermatids and testicular sperm WAVE1 localized to the mitochondrial sheath. Following epididymal passage, WAVE1 was found exclusively on the mitochondrial sheath, suggesting that the protein may function in this region. WAVE1 and PKA RII co-localized along the mitochondrial sheath, PKA RII concentrates in the mid-piece, and RAC1 associated with the post-acrosomal region and the connecting piece. The distribution of WAVE1, PKA RII and RAC1 is conserved in mature mouse, bull, baboon and human sperm. CONCLUSIONS The data support the possibility of a functional signalling unit established by WAVE1 and its associated proteins in the mid-piece of maturing sperm.
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Affiliation(s)
- Vanesa Y Rawe
- Pittsburgh Development Center, Magee--Women's Research Institute, Department of Obstetrics, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
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20
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Dwivedi Y, Rizavi HS, Shukla PK, Lyons J, Faludi G, Palkovits M, Sarosi A, Conley RR, Roberts RC, Tamminga CA, Pandey GN. Protein kinase A in postmortem brain of depressed suicide victims: altered expression of specific regulatory and catalytic subunits. Biol Psychiatry 2004; 55:234-43. [PMID: 14744463 DOI: 10.1016/j.biopsych.2003.11.003] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND We recently reported reduced [3H]cyclic adenosine monophosphate binding and catalytic activity of protein kinase A in prefrontal cortex of depressed suicide victims. Here we examined the molecular basis of these alterations and whether these findings can be replicated in another cohort. METHODS Prefrontal cortex from depressed suicide victims and nonpsychiatric controls were obtained from the Lenhossek Human Brain Program, Budapest and the Maryland Brain Collection Program. [3H]cyclic adenosine monophosphate binding and protein kinase A activity were determined by radioligand binding and enzymatic assay, respectively. Expression of catalytic and regulatory subunits was determined by quantitative reverse transcription polymerase chain reaction and Western blot, respectively. RESULTS [3H]cyclic adenosine monophosphate binding and total and endogenous protein kinase A activity were significantly decreased in membrane and cytosol fractions of prefrontal cortex of depressed suicide victims from the Budapest cohort, with a similar magnitude (33%-40% reduction) as reported for the Maryland cohort. In both cohorts, selective reduction (36%-41%) in mRNA and protein expression of the regulatory RIIbeta and the catalytic Cbeta was observed. CONCLUSIONS Our results suggest abnormalities in [3H]cyclic adenosine monophosphate binding and catalytic activity kinase A in brain of depressed suicide victims, which could be due to reduced expression of RIIbeta and Cbeta. These abnormalities in PKA may be critical in the pathophysiology of depression.
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Affiliation(s)
- Yogesh Dwivedi
- Psychiatric Institute, Department of Psychiatry, University of Illinois at Chicago, 1601 W. Taylor Street, Chicago, IL 60612, USA
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21
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Méndez E, Maeland M, Skålhegg BS, Planas JV. Activation of the cAMP-dependent protein kinase signaling pathway by luteinizing hormone in trout theca layers. Mol Cell Endocrinol 2003; 205:11-20. [PMID: 12890563 DOI: 10.1016/s0303-7207(03)00208-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
In the fish ovary, LH is the main factor regulating the production of steroids during the periovulatory period and its effects are believed to be mediated, at least partially, through the cAMP-dependent protein kinase (PKA) signaling pathway. However, there is no direct evidence for the presence of PKA in the fish ovary nor on the regulation of its activity by fish LH. Here, we show the identification of regulatory (R) and catalytic (C) subunits of PKA in trout theca cells by immunoblotting. DEAE-cellulose chromatography of theca cell extracts indicated the presence of PKA type I and II and showed that trout theca cells display PKA-specific phosphotransferase and cAMP-binding activities. Salmon LH (sLH) stimulated PKA activity and increased the levels of immunoreactive RIIalpha, RIIbeta and C subunits in trout theca layers. These observations, coupled with the sLH-dependent decrease in the half-life of the C subunit, as shown by pulse-chase experiments, strongly suggest that sLH activates PKA in trout theca cells. Furthermore, our results suggest that ovarian PKA activity and its regulation by LH has been well conserved from fish to humans.
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Affiliation(s)
- Eva Méndez
- Departament de Fisiologia, Facultat de Biologia, Universitat de Barcelona, Av. Diagonal 645, 08028 Barcelona, Spain
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22
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Chin KV, Yang WL, Ravatn R, Kita T, Reitman E, Vettori D, Cvijic ME, Shin M, Iacono L. Reinventing the wheel of cyclic AMP: novel mechanisms of cAMP signaling. Ann N Y Acad Sci 2002; 968:49-64. [PMID: 12119267 DOI: 10.1111/j.1749-6632.2002.tb04326.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Mechanisms of cAMP signal transduction have been thoroughly investigated for more than 40 years. From the binding of hormonal ligands to their receptors on the outer surface of the plasma membrane to the cytoplasmic activation of effectors, the ensuing cAMP signaling cascades and the nuclear gene regulatory functions, coupled with the structural elucidation of the cAMP-dependent protein kinase (PKA) and in vivo functional characterizations of each of the components of PKA by homologous recombination gene targeting, our understanding of cAMP-mediated signal transduction has reached its pinnacle. Despite this trove of knowledge, some recent findings have emerged that suggest hitherto novel and alternative mechanisms of cAMP action that could increase the signaling bandwidth of cAMP and PKA in cell growth and transcriptional regulation. This article attempts to review some of these novel and unconventional mechanisms of cAMP and PKA signaling, and to generate further enthusiasm in investigating and validating these new frontiers of the cAMP signal transduction pathway.
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Affiliation(s)
- Khew-Voon Chin
- Department of Medicine and Pharmacology and The Cancer Institute of New Jersey, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, New Brunswick, New Jersey 08901, USA.
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23
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Dahle MK, Knutsen HK, Taskén KA, Pilz R, Taskén K. Cyclic AMP regulates expression of the RI alpha subunit of cAMP-dependent protein kinase through an alternatively spliced 5' UTR. EUROPEAN JOURNAL OF BIOCHEMISTRY 2001; 268:5920-9. [PMID: 11722580 DOI: 10.1046/j.0014-2956.2001.02542.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The present study examines novel mechanisms that regulate levels of the RI alpha subunit of cAMP-dependent protein kinase. We found that RI alpha protein is induced threefold by 8-(4-chlorophenyl)thio-cAMP in hormone responsive rat Sertoli cells, while total RI alpha mRNA is not correspondingly induced. Two RI alpha mRNA isoforms with different 5' untranslated sequences (RI alpha 1a and RI alpha 1b) are produced from the RI alpha gene in Sertoli cells. Deletion/mutation analysis of the cAMP-response-element-containing promoter upstream of the RI alpha exon 1b revealed that while mutation of the cAMP response element had no effects on cAMP-mediated induction, a 73-bp region of the RI alpha exon 1b itself conferred a fivefold to eightfold induction of reporter activity to homologous and heterologous promoters. The responsiveness of this region was dependent on a sense orientation downstream of the promoter start sites and had no effect on reporter mRNA, indicating that the cAMP-mediated induction occurs at the post-transcriptional level. Modeling of the RI alpha 1b 5' UTR secondary structure revealed a 5' CAP-proximal, strong stem-loop presenting an element similar to multiple start-site element downstream-1 (GCTCGG) in the loop region. RNA-EMSAs performed with the labeled RI alpha 1b 5' UTR showed stabilization of a protein/RNA complex in extracts from 8-(4-chlorophenyl)thio-cAMP stimulated Sertoli cells. This complex was abolished by mutation of the multiple start-site element downstream-1-like element. Our findings indicate that there is a cAMP-mediated induction of RI alpha expression at the post-transcriptional level, dependent on the 5' UTR of RI alpha 1b mRNA.
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Affiliation(s)
- M K Dahle
- Department of Medical Biochemistry, Institute of Basic Medical Sciences, University of Oslo, Norway.
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24
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San Agustin JT, Witman GB. Differential expression of the C(s) and Calpha1 isoforms of the catalytic subunit of cyclic 3',5'-adenosine monophosphate-dependent protein kinase testicular cells. Biol Reprod 2001; 65:151-64. [PMID: 11420235 DOI: 10.1095/biolreprod65.1.151] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The amino terminus of the sperm cAMP-dependent protein kinase catalytic subunit (termed C(s)) differs from that of the Calpha1 isoform expressed in most tissues due to the use of alternative transcripts of the Calpha gene. Both Calpha1 and C(s) transcripts are present in testis; C(s) is expressed specifically in spermatogenic cells and is the only C isoform detected in mature sperm. Immunohistochemistry of mouse testis using antibodies specific for C(s) and Calpha1 now shows that Calpha1 is present in somatic testicular cells, spermatogonia, and preleptotene spermatocytes but not in cells that are in later stages of spermatogenesis. In contrast, C(s) is expressed only in midpachytene and later stage spermatocytes and in spermatids. Therefore, C(s) and Calpha1 expression do not overlap. Immunofluorescence microscopic localization of C(s) in murine and ovine sperm reveals that C(s) is located primarily in sperm tail components, including the midpiece mitochondria and the axoneme. Quantitative analysis of Western blots indicates that individual ovine sperm contain approximately 4 x 10(5) molecules of C(s), a seemingly large number for a protein that acts catalytically.
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Affiliation(s)
- J T San Agustin
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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25
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Dahle MK, Reinton N, Orstavik S, Taskén KA, Taskén K. Novel alternatively spliced mRNA (1c) of the protein kinase A RIα subunit is implicated in haploid germ cell specific expression. Mol Reprod Dev 2001; 59:11-6. [PMID: 11335941 DOI: 10.1002/mrd.1001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
By using 5' RACE on rat testis cDNA we identified three alternatively spliced mRNAs of the RIalpha subunit of cAMP-dependent protein kinase that differed in their 5' untranslated regions. Two of these 5'-regions showed similarity with the human RIalpha exons 1a and 1b, while the third (1c) constituted a novel mRNA splice variant. Northern blot analysis showed that the 1c mRNA was specifically expressed in testis and only in postmeiotic germ cells. In contrast, the RIalpha 1b and RIalpha 1a mRNAs were present both in premeiotic germ cells and somatic cells of the testis, and the expression of both RIalpha 1a and 1b mRNAs were stimulated by cAMP in Sertoli cells. In sperm, the RIalpha protein was expressed after meiosis, and targeted to various subcellular structures via anchoring proteins. The RIalpha 1c haploid-specific mRNA, therefore, may be important for the regulation of RIalpha expression in sperm.
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Affiliation(s)
- M K Dahle
- Institute of Medical Biochemistry, University of Oslo, Oslo, Norway.
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26
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Agustin JT, Wilkerson CG, Witman GB. The unique catalytic subunit of sperm cAMP-dependent protein kinase is the product of an alternative Calpha mRNA expressed specifically in spermatogenic cells. Mol Biol Cell 2000; 11:3031-44. [PMID: 10982398 PMCID: PMC14973 DOI: 10.1091/mbc.11.9.3031] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
cAMP-dependent protein kinase has a central role in the control of mammalian sperm capacitation and motility. Previous protein biochemical studies indicated that the only cAMP-dependent protein kinase catalytic subunit (C) in ovine sperm is an unusual isoform, termed C(s), whose amino terminus differs from those of published C isoforms of other species. Isolation and sequencing of cDNA clones encoding ovine C(s) and Calpha1 (the predominant somatic isoform) now reveal that C(s) is the product of an alternative transcript of the Calpha gene. C(s) cDNA clones from murine and human testes also were isolated and sequenced, indicating that C(s) is of ancient origin and widespread in mammals. In the mouse, C(s) transcripts were detected only in testis and not in any other tissue examined, including ciliated tissues and ovaries. Finally, immunohistochemistry of the testis shows that C(s) first appears in pachytene spermatocytes. This is the first demonstration of a cell type-specific expression for any C isoform. The conservation of C(s) throughout mammalian evolution suggests that the unique structure of C(s) is important in the subunit's localization or function within the sperm.
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Affiliation(s)
- J T Agustin
- Department of Cell Biology, University of Massachusetts Medical School, Worcester, Massachusetts 01655, USA
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27
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Reinton N, Orstavik S, Haugen TB, Jahnsen T, Taskén K, Skålhegg BS. A novel isoform of human cyclic 3',5'-adenosine monophosphate-dependent protein kinase, c alpha-s, localizes to sperm midpiece. Biol Reprod 2000; 63:607-11. [PMID: 10906071 DOI: 10.1095/biolreprod63.2.607] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Using rapid amplification of cDNA ends, a cDNA encoding a novel splice variant of the human C alpha catalytic subunit of cAMP-dependent protein kinase (PKA) was identified. The novel isoform differed only in the N-terminal part of the deduced amino acid sequence, corresponding to the part encoded by exon 1 in the previously characterized murine C alpha gene. Sequence comparison revealed similarity to an ovine C alpha variant characterized by protein purification and micropeptide sequencing, C alpha-s, identifying the cloned human cDNA as the C alpha-s isoform. The C alpha-s mRNA was expressed exclusively in human testis and expression in isolated human pachytene spermatocytes was demonstrated. The C alpha-s protein was present in ejaculated human sperm, and immunofluorescent labeling with a C alpha-s-specific antibody indicated that C alpha-s was localized in the midpiece region of the spermatozoon. The majority of C alpha-s was particulate and could not be released from the sperm midpiece by cAMP treatment alone. Furthermore, detergent extraction solubilized approximately two-thirds of the C alpha-s pool, indicating interaction both with detergent-resistant cytoskeletal and membrane structures. In addition, we recently identified the regulatory subunit isoforms RI alpha, RII alpha, and an A-kinase anchoring protein, hAKAP220 in this region in sperm that could target C alpha-s. This novel C alpha-s splice variant appeared to have an independent anchor in the human sperm midpiece as it could not be completely solubilized even in the presence of both detergent and cAMP.
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Affiliation(s)
- N Reinton
- Institute of Medical Biochemistry, University of Oslo, N-0317 Oslo, Norway
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28
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Reinton N, Collas P, Haugen TB, Skâlhegg BS, Hansson V, Jahnsen T, Taskén K. Localization of a novel human A-kinase-anchoring protein, hAKAP220, during spermatogenesis. Dev Biol 2000; 223:194-204. [PMID: 10864471 DOI: 10.1006/dbio.2000.9725] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Using a combination of protein kinase A type II overlay screening, rapid amplification of cDNA ends, and database searches, a contig of 9923 bp was assembled and characterized in which the open reading frame encoded a 1901-amino-acid A-kinase-anchoring protein (AKAP) with an apparent SDS-PAGE mobility of 220 kDa, named human AKAP220 (hAKAP220). The hAKAP220 amino acid sequence revealed high similarity to rat AKAP220 in the 1167 C-terminal residues, but contained 727 residues in the N-terminus not present in the reported rat AKAP220 sequence. The hAKAP220 mRNA was expressed at high levels in human testis and in isolated human pachytene spermatocytes and round spermatids. The hAKAP220 protein was present in human male germ cells and mature sperm. Immunofluorescent labeling with specific antibodies indicated that hAKAP220 was localized in the cytoplasm of premeiotic pachytene spermatocytes and in the centrosome of developing postmeiotic germ cells, while a midpiece/centrosome localization was found in elongating spermatocytes and mature sperm. The hAKAP220 protein together with a fraction of PKA types I and II and protein phosphatase I was resistant to detergent extraction of sperm tails, suggesting an association with cytoskeletal structures. In contrast, S-AKAP84/D-AKAP1, which is also present in the midpiece, was extracted under the same conditions. Anti-hAKAP220 antisera coimmunoprecipitated both type I and type II regulatory subunits of PKA in human testis lysates, indicating that hAKAP220 interacts with both classes of R subunits, either through separate or through a common binding motif(s).
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Affiliation(s)
- N Reinton
- Institute of Medical Biochemistry, University of Oslo, Oslo, N-0317, Norway
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29
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Desseyn JL, Burton KA, McKnight GS. Expression of a nonmyristylated variant of the catalytic subunit of protein kinase A during male germ-cell development. Proc Natl Acad Sci U S A 2000; 97:6433-8. [PMID: 10841548 PMCID: PMC18620 DOI: 10.1073/pnas.97.12.6433] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The catalytic subunits of protein kinase A are transcribed in all mouse tissues from two distinct genes that code for the Calpha and Cbeta isoforms. Alternative promoters exist for the Cbeta gene that are used in a tissue-specific fashion and give rise to variants that differ in their amino-terminal sequences. We have characterized an alternative promoter that is present in the first intron of the Calpha gene and is transcriptionally active in male germ cells. Transcription from this promoter is coincident with the appearance of pachytene spermatocytes and leads to a Calpha protein (Calpha2) that contains a distinctive 7 amino acid amino-terminus differing from the 14 amino acid amino-terminus of Calpha1. The Calpha2 protein does not contain the myristylation signal present on Calpha1 and migrates at a lower molecular weight on SDS/PAGE gels. By Western blotting, we estimate that most or all of the Calpha protein present in mature sperm is Calpha2. The amino-terminal sequence of Calpha2 is similar to that of ovine sperm C as previously reported [San Agustin, J. T., Leszyk, J. D., Nuwaysir, L. M. & Witman, G. B. (1998) J. Biol. Chem. 273, 24874-24883], and we show by cDNA cloning that human sperm also express a highly related Calpha2 homolog. The Calpha2 subunit forms holoenzymes with either RIIalpha or RIalpha, and both activate at the same concentration of cyclic nucleotide. Because protein kinase A is thought to play a pivotal role in sperm motility and capacitation, the distinctive biochemical properties of the unmyristylated Calpha2 may be essential for fertility in the male.
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Affiliation(s)
- J L Desseyn
- Department of Pharmacology, University of Washington, Seattle, WA 98195-7750, USA
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30
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Burton KA, Treash-Osio B, Muller CH, Dunphy EL, McKnight GS. Deletion of type IIalpha regulatory subunit delocalizes protein kinase A in mouse sperm without affecting motility or fertilization. J Biol Chem 1999; 274:24131-6. [PMID: 10446185 DOI: 10.1074/jbc.274.34.24131] [Citation(s) in RCA: 72] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyclic AMP stimulates sperm motility in a variety of mammalian species, but the molecular details of the intracellular signaling pathway responsible for this effect are unclear. The type IIalpha isoform of protein kinase A (PKA) is induced late in spermatogenesis and is thought to localize PKA to the flagellar apparatus where it binds cAMP and stimulates motility. A targeted disruption of the type IIalpha regulatory subunit (RIIalpha) gene allowed us to examine the role of PKA localization in sperm motility and fertility. In wild type sperm, PKA is found primarily in the detergent-resistant particulate fraction and localizes to the mitochondrial-containing midpiece and the principal piece. In mutant sperm, there is a compensatory increase in RIalpha protein and a dramatic relocalization of PKA such that the majority of the holoenzyme now appears in the soluble fraction and colocalizes with the cytoplasmic droplet. Unexpectedly the RIIalpha mutant mice are fertile and have no significant changes in sperm motility. Our results demonstrate that the highly localized pattern of PKA seen in mature sperm is not essential for motility or fertilization.
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Affiliation(s)
- K A Burton
- Department of Pharmacology, University of Washington School of Medicine, Seattle, Washington 98195-7750, USA
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31
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Loveland KL, Herszfeld D, Chu B, Rames E, Christy E, Briggs LJ, Shakri R, de Kretser DM, Jans DA. Novel low molecular weight microtubule-associated protein-2 isoforms contain a functional nuclear localization sequence. J Biol Chem 1999; 274:19261-8. [PMID: 10383434 DOI: 10.1074/jbc.274.27.19261] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Known high and low molecular weight (LMW) MAP2 protein isoforms result from alternative splicing of the MAP2 gene. Contrary to previous reports that MAP2 is neural-specific, we recently identified MAP2 mRNA and protein in somatic and germ cells of rat testis, and showed the predominant testicular isoform is LMW. Although cytoplasmic in neural tissue, MAP2 appeared predominantly nuclear in germ cells using immunohistochemistry. We sought to determine whether this unexpected localization was due to the inclusion of exon 10 within novel LMW MAP2 isoforms. Normally excluded from the LMW MAP2c, exon 10 harbors a putative CcN motif, comprising a nuclear localization sequence (NLS) flanked by regulatory phosphorylation sites for protein kinase CK2 and cdc2 kinase. Characterization of MAP2 mRNA in adult and immature brain and testis, by reverse transcriptase-polymerase chain reaction/Southern analysis and Northern blot, identified novel LMW forms containing exons 10 and 11, previously detected only in high molecular weight MAP2a and 2b. The MAP2 NLS targeted a large heterologous protein to the nucleus, as demonstrated using bacterially expressed MAP2-CcN-beta-galactosidase fusion protein and an in vitro nuclear import assay. Antibodies raised against the fusion protein produced a testicular immunohistochemical staining pattern correlating with MAP2 protein distribution in the nucleus of most germ cells, and precipitated both approximately 70-kDa and >220-kDa proteins recognized by the commercial MAP2-specific HM2 monoclonal antibody, supporting our hypothesis of a novel LMW MAP2 isoform. These results demonstrate the presence of a functional NLS in MAP2 and indicate that novel LMW MAP2 isoforms may be targeted to the nucleus in both neural and non-neuronal tissues.
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Affiliation(s)
- K L Loveland
- Institute of Reproduction & Development, Monash University, Clayton, Victoria 3168, Australia.
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Behr R, Weinbauer GF. Germ cell-specific cyclic adenosine 3',5'-monophosphate response element modulator expression in rodent and primate testis is maintained despite gonadotropin deficiency. Endocrinology 1999; 140:2746-54. [PMID: 10342865 DOI: 10.1210/endo.140.6.6764] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
cAMP response element modulator (CREM) is an important component of the cAMP-mediated signaling pathway and is essential for differentiation of haploid male germ cells. In the rodent, testicular expression of CREM is believed to be controlled by FSH. We studied the expression pattern of CREM and gonadotropic control in the nonhuman primate and rodent testis. Adult cynomolgus monkeys (Macaca fascicularis) received daily either vehicle or the potent GnRH antagonist (ANT) cetrorelix for periods of 25 and 56 days. Rats were also exposed to vehicle or ANT for periods of 14 and 42 days. ANT treatment suppressed pituitary gonadotropin secretion, reduced testis size, and altered spermatogenesis. A rabbit polyclonal antibody raised against recombinant CREM tau and reacting with CREM alpha, -beta, -gamma, -tau1, and -tau2 at similar affinities was used for immunocytochemistry and Western blotting. CREM expression was seen in round spermatids, with highest levels during spermatogenic stages V-VII, but declined with progression of spermatid development in the primate. Similar observations were made for the rat testis. Thus, CREM expression was maximal at the onset of acrosome formation and was low or undetectable upon initiation of spermatid elongation in both species. A weak, but specific, CREM signal was seen in mid- to late pachytene spermatocytes and during meiotic division in both species. After ANT exposure, the germ cell- and stage-specific pattern of CREM expression was quantitatively retained at all time points and in both species. Northern and Western blot analysis confirmed the maintenance of testicular CREM expression despite 25 days of ANT treatment. A retrospective immunocytochemical analysis of rat testes 14 days posthypophysectomy revealed CREM signals in round spermatids. These findings demonstrate that the testicular expression of CREM is not entirely dependent on gonadotropic hormones but, rather, on the maturational stage of haploid round germ cells.
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Affiliation(s)
- R Behr
- Institute of Reproductive Medicine of the University, Munster, Germany
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Hansson V, Skålhegg BS, Taskén K. Cyclic-AMP-dependent protein kinase (PKA) in testicular cells. Cell specific expression, differential regulation and targeting of subunits of PKA. J Steroid Biochem Mol Biol 1999; 69:367-78. [PMID: 10419014 DOI: 10.1016/s0960-0760(99)00077-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
LH and FSH regulate via cyclic adenosine 3'5' cyclic monophosphate (cAMP) and cAMP-dependent protein kinase (PKA), steroid biosynthesis is Leydig and Sertoli cells, respectively. Cyclic AMP also regulates a number of different cellular processes such as cell growth and differentiation, ion channel conductivity, synaptic release of neurotransmitters, and gene transcription. The principle intracellular target for cAMP in mammalian cells is the PKA. The fact that this broad specificity protein kinase mediates a number of discrete physiological responses following cAMP engagement, has raised the question of how specificity is maintained in the cAMP/PKA system. Here we describe features of this signaling pathway that may contribute to explain how differential effects of cAMP may be contributed to features of the PKA signaling pathway.
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Affiliation(s)
- V Hansson
- Institute of Medical Biochemistry, University of Oslo, Norway
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Visconti PE, Johnson LR, Oyaski M, Fornés M, Moss SB, Gerton GL, Kopf GS. Regulation, localization, and anchoring of protein kinase A subunits during mouse sperm capacitation. Dev Biol 1997; 192:351-63. [PMID: 9441673 DOI: 10.1006/dbio.1997.8768] [Citation(s) in RCA: 147] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The molecular basis of mammalian sperm capacitation, defined as those biochemical and functional changes that render the sperm competent to fertilize the egg, is poorly understood. This extratesticular maturational process is accompanied by the activation of a unique signal transduction pathway involving the cAMP-dependent up-regulation of protein tyrosine phosphorylation presumably through the activation of protein kinase A (PK-A). We demonstrate in this report that capacitation of cauda epididymal mouse sperm in vitro was accompanied by a time-dependent increase in PK-A activity. This increase in PK-A activity did not occur in a medium that does not support capacitation. While PK-A catalytic and RI/RII regulatory subunits, as well as PK-A enzyme activity, were found in both the Triton X-100-soluble and -insoluble fractions of the sperm, the increase in PK-A activity accompanying capacitation was associated with enzyme activity found in the soluble fraction. Moreover, the regulatory and catalytic subunits of PK-A were observed by indirect immunofluorescence to be present throughout the head, midpiece, and principal piece of the sperm. Thus, PK-A appears to be functional in multiple compartments of this highly differentiated cell. A fraction of the Triton X-100-insoluble PK-A is presumably tethered by AKAP82, the major protein of the fibrous sheath of the sperm flagellum which anchors and compartmentalizes PK-A to the cytoskeleton via the RII subunit of PK-A. Using various recombinant truncated AKAP82 constructs in a gel overlay assay, the RII subunit-binding domain of this protein was mapped to a 57-amino-acid residue region at its N-terminus. Computer analysis revealed a 14-amino-acid region that resembled the RII-binding domains of other A Kinase Anchor Proteins. A synthetic peptide corresponding to this domain inhibited AKAP82-RII binding in a gel overlay assay, providing further support that AKAP82 is an anchoring protein for the subcellular localization of PK-A in the mouse sperm fibrous sheath. This work, along with previous findings that cAMP is a key intermediary second messenger in regulating protein tyrosine phosphorylation and capacitation, further supports the importance of PK-A in these processes and necessitates a further understanding of the contribution of both the soluble and insoluble forms of PK-A, as well as AKAP82, to sperm function.
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Affiliation(s)
- P E Visconti
- Department of Obstetrics and Gynecology, University of Pennsylvania Medical Center, Philadelphia 19104-6080, USA
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Taskén K, Skålhegg BS, Taskén KA, Solberg R, Knutsen HK, Levy FO, Sandberg M, Orstavik S, Larsen T, Johansen AK, Vang T, Schrader HP, Reinton NT, Torgersen KM, Hansson V, Jahnsen T. Structure, function, and regulation of human cAMP-dependent protein kinases. ADVANCES IN SECOND MESSENGER AND PHOSPHOPROTEIN RESEARCH 1997; 31:191-204. [PMID: 9344252 DOI: 10.1016/s1040-7952(97)80019-5] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
A large number of hormones, neurotransmitters, and other signaling substances that bind to G-protein-coupled cell-surface receptors have their signals converge at one sole second messenger, cAMP. The question of how specificity can be maintained in a signal-transduction system in which many extracellular signals leading to a vast array of intracellular responses are all mediated through one second-messenger system has been the subject of thorough investigation and a great deal of speculation. An increasing number of cAK isozymes, consisting of homo- or heterodimers of R subunits (RIalpha, RIbeta, RIIalpha, RIIbeta) with associated catalytic subunits (C alpha, Cbeta, Cgamma), may, at least in part, explain this specificity. The various cAK isozymes display distinct biochemical properties, and the heterogeneous subunits of cAK reveal cell-specific expression and differential regulation at the level of gene transcription, mRNA stability, and protein stability in response to a wide range of hormones and other signaling substances. The existence of a number of anchoring proteins specific to either RIIalpha or RIIbeta, and which localize cAKII isozymes toward distinct substrates at defined subcellular loci, strongly supports the idea that specific functions can be assigned to the various cAK isozymes. The demonstration that selective activation of cAKI is necessary and sufficient for cAMP-mediated inhibition of T-cell proliferation, and the observation that T-cell activation is associated with redistribution and colocalization of cAKI to the TCR, is also compatible with the notion of isozyme-specific effects.
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Affiliation(s)
- K Taskén
- Institute of Medical Biochemistry, University of Oslo, Norway
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Chen Q, Lin RY, Rubin CS. Organelle-specific targeting of protein kinase AII (PKAII). Molecular and in situ characterization of murine A kinase anchor proteins that recruit regulatory subunits of PKAII to the cytoplasmic surface of mitochondria. J Biol Chem 1997; 272:15247-57. [PMID: 9182549 DOI: 10.1074/jbc.272.24.15247] [Citation(s) in RCA: 122] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Experiments were designed to test the idea that A kinase anchor proteins (AKAPs) tether regulatory subunits (RII) of protein kinase AII (PKAII) isoforms to surfaces of organelles that are bounded by phospholipid bilayers. S-AKAP84, one of three RII-binding proteins encoded by a single-copy murine gene, was studied as a prototypic organelle-associated AKAP. When S-AKAP84 was expressed in HEK293 cells, the anchor protein was targeted to mitochondria and excluded from other cell compartments. The RII tethering site is located in the cytoplasm adjacent to the mitochondrial surface. Endogenous RII subunits are not associated with mitochondria isolated from control cells. Expression of S-AKAP84 in transfected HEK293 cells triggered a redistribution of 15% of total RII to mitochondria. Thus, the tethering region of the organelle-inserted anchor protein is properly oriented and avidly binds RII (PKAII) isoforms in intact cells. Two critical domains in S-AKAP84 were mapped. Residues 1 to 30 govern insertion of the polypeptide into the outer mitochondrial membrane; amino acids 306-325 constitute the RII-binding site. Properties established for S-AKAP84 in vitro and in situ strongly suggest that a physiological function of this protein is to concentrate and immobilize RII (PKAII) isoforms at the cytoplasmic face of a phospholipid bilayer.
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Affiliation(s)
- Q Chen
- Department of Molecular Pharmacology, Atran Laboratories, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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Lin RY, Moss SB, Rubin CS. Characterization of S-AKAP84, a novel developmentally regulated A kinase anchor protein of male germ cells. J Biol Chem 1995; 270:27804-11. [PMID: 7499250 DOI: 10.1074/jbc.270.46.27804] [Citation(s) in RCA: 150] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
In mammalian spermatozoa, most of the type II alpha isoform of cAMP-dependent protein kinase (PKAII alpha) is anchored at the cytoplasmic surface of a specialized array of mitochondria in the flagellar cytoskeleton. This places the catalytic subunits of PKAII alpha in proximity with potential target substrates in the cytoskeleton. The mechanism by which PKAII alpha is anchored at the outer surface of germ cell mitochondria has not been elucidated. We now report the cloning of a cDNA that encodes a novel, germ cell A kinase anchor protein (AKAP) designated S-AKAP84. S-AKAP84 comprises 593 amino acids and contains a centrally located domain that avidly binds regulatory subunits (RII alpha and RII beta) of PKAII alpha and PKAII beta. The 3.2-kilobase S-AKAP84 mRNA and the cognate S-AKAP84 RII binding protein are expressed principally in the male germ cell lineage. Expression of S-AKAP84 is tightly regulated during development. The protein accumulates as spermatids undergo nuclear condensation and tail elongation. The timing of S-AKAP84 expression is correlated with the de novo accumulation of RII alpha and RII beta subunits and the migration of mitochondria from the cytoplasm (round spermatids) to the cytoskeleton (midpiece in elongating spermatids). Residues 1-30 at the NH2 terminus of S-AKAP84 constitute a putative signal/anchor sequence that may target the protein to the outer mitochondrial membrane. Immunofluorescence analysis demonstrated that S-AKAP84 is co-localized with mitochondria in the flagellum.
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Affiliation(s)
- R Y Lin
- Department of Molecular Pharmacology, Atran Laboratories, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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