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An unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the C. elegans putative aminophospholipid translocases.

Lyssenko NN, Miteva Y, Gilroy S, Hanna-Rose W, Schlegel RA - BMC Dev. Biol. (2008)

Bottom Line: Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system.Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant.These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. lyssenn@ccf.org

ABSTRACT

Background: P-type ATPases in subfamily IV are exclusively eukaryotic transmembrane proteins that have been proposed to directly translocate the aminophospholipids phosphatidylserine and phosphatidylethanolamine from the exofacial to the cytofacial monolayer of the plasma membrane. Eukaryotic genomes contain many genes encoding members of this subfamily. At present it is unclear why there are so many genes of this kind per organism or what individual roles these genes perform in organism development.

Results: We have systematically investigated expression and developmental function of the six, tat-1 through 6, subfamily IV P-type ATPase genes encoded in the Caenorhabditis elegans genome. tat-5 is the only ubiquitously-expressed essential gene in the group. tat-6 is a poorly-transcribed recent duplicate of tat-5. tat-2 through 4 exhibit tissue-specific developmentally-regulated expression patterns. Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system. The two are also expressed in the uterus, during spermatogenesis and in the fully-formed spermatheca. tat-2 alone is expressed in the pharyngeal gland cells, the excretory system and a few cells of the developing vulva. The expression pattern of tat-3 is almost completely different from those of tat-2 and tat-4. tat-3 expression is detectable in the steroidogenic tissues: the hypodermis and the XXX cells, as well as in most cells of the pharynx (except gland), various tissues of the reproductive system (except uterus and spermatheca) and seam cells. Deletion of tat-1 through 4 individually interferes little or not at all with the regular progression of organism growth and development under normal conditions. However, tat-2 through 4 become essential for reproductive growth during sterol starvation.

Conclusion: tat-5 likely encodes a housekeeping protein that performs the proposed aminophospholipid translocase function routinely. Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant. Expression patterns and the sterol deprivation hypersensitivity deletion phenotype of tat-2 through 4 suggest that these genes carry out subtle metabolic functions, such as fine-tuning sterol metabolism in digestive or steroidogenic tissues. These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

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tat-2 reporter expression pattern. The 5' end of the tat-2 locus, locations of the deleted regions in tm1634 and tm1773 mutants (bars) and structure of the tat-2 expression cassette (A). Expression of the tat-2 reporter in the lcIs982.4.2 line in embryos (B), in the intestine of L2 larvae (C) and in gland cells of the pharynx, the pharyngeal-intestinal valve, the excretory gland cell and the intestine of a young adult (D). GFP fluorescence in the lcEx982.2.4.5 line in the excretory pore and excretory canal cells (E). Reporter signal outlining the vulF cells in early lcIs982.4.2 L4 larvae (the third frame in the series shows an overlay of the pseudocolored UV image onto the bright light image, both enlarged with re-sampling using Photoshop; dashes extend along the contact surface between the two tissues) (F). tat-2 reporter expression during spermatogenesis (G) and in adult spermatheca (H) of lcIs982.4.2 animals. Abbreviations: eg – excretory gland cell; epc – excretory pore cell; g – pharyngeal gland cell; ga – gonad arm; ph – pharynx; pv – pharyngeal-intestinal valve; oo – oocyte; r – rectum; sp – spermatheca.
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Figure 4: tat-2 reporter expression pattern. The 5' end of the tat-2 locus, locations of the deleted regions in tm1634 and tm1773 mutants (bars) and structure of the tat-2 expression cassette (A). Expression of the tat-2 reporter in the lcIs982.4.2 line in embryos (B), in the intestine of L2 larvae (C) and in gland cells of the pharynx, the pharyngeal-intestinal valve, the excretory gland cell and the intestine of a young adult (D). GFP fluorescence in the lcEx982.2.4.5 line in the excretory pore and excretory canal cells (E). Reporter signal outlining the vulF cells in early lcIs982.4.2 L4 larvae (the third frame in the series shows an overlay of the pseudocolored UV image onto the bright light image, both enlarged with re-sampling using Photoshop; dashes extend along the contact surface between the two tissues) (F). tat-2 reporter expression during spermatogenesis (G) and in adult spermatheca (H) of lcIs982.4.2 animals. Abbreviations: eg – excretory gland cell; epc – excretory pore cell; g – pharyngeal gland cell; ga – gonad arm; ph – pharynx; pv – pharyngeal-intestinal valve; oo – oocyte; r – rectum; sp – spermatheca.

Mentions: Two integrated and three extrachromosomal transgenic lines carrying tat-2::nls::gfp expression cassettes were made by particle bombardment (Figure 4A). With the exception of a few instances of ectopic transcription in the extrachromosomal lines, all five generally exhibit nearly identical patterns of reporter expression. Curiously, GFP fluorescence in the tat-2::nls::gfp transgenic nematodes emanates not from the nucleus, as would be expected with an NLS-tagged reporter, but mostly from the plasma membrane region (Figure 4B–H). Apparently, the short TAT-2-coding fragment that is retained in the tat-2 expression cassette "overpowers" the NLS and directs the chimeric reporter peptide to the plasma membrane compartment.


An unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the C. elegans putative aminophospholipid translocases.

Lyssenko NN, Miteva Y, Gilroy S, Hanna-Rose W, Schlegel RA - BMC Dev. Biol. (2008)

tat-2 reporter expression pattern. The 5' end of the tat-2 locus, locations of the deleted regions in tm1634 and tm1773 mutants (bars) and structure of the tat-2 expression cassette (A). Expression of the tat-2 reporter in the lcIs982.4.2 line in embryos (B), in the intestine of L2 larvae (C) and in gland cells of the pharynx, the pharyngeal-intestinal valve, the excretory gland cell and the intestine of a young adult (D). GFP fluorescence in the lcEx982.2.4.5 line in the excretory pore and excretory canal cells (E). Reporter signal outlining the vulF cells in early lcIs982.4.2 L4 larvae (the third frame in the series shows an overlay of the pseudocolored UV image onto the bright light image, both enlarged with re-sampling using Photoshop; dashes extend along the contact surface between the two tissues) (F). tat-2 reporter expression during spermatogenesis (G) and in adult spermatheca (H) of lcIs982.4.2 animals. Abbreviations: eg – excretory gland cell; epc – excretory pore cell; g – pharyngeal gland cell; ga – gonad arm; ph – pharynx; pv – pharyngeal-intestinal valve; oo – oocyte; r – rectum; sp – spermatheca.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2572054&req=5

Figure 4: tat-2 reporter expression pattern. The 5' end of the tat-2 locus, locations of the deleted regions in tm1634 and tm1773 mutants (bars) and structure of the tat-2 expression cassette (A). Expression of the tat-2 reporter in the lcIs982.4.2 line in embryos (B), in the intestine of L2 larvae (C) and in gland cells of the pharynx, the pharyngeal-intestinal valve, the excretory gland cell and the intestine of a young adult (D). GFP fluorescence in the lcEx982.2.4.5 line in the excretory pore and excretory canal cells (E). Reporter signal outlining the vulF cells in early lcIs982.4.2 L4 larvae (the third frame in the series shows an overlay of the pseudocolored UV image onto the bright light image, both enlarged with re-sampling using Photoshop; dashes extend along the contact surface between the two tissues) (F). tat-2 reporter expression during spermatogenesis (G) and in adult spermatheca (H) of lcIs982.4.2 animals. Abbreviations: eg – excretory gland cell; epc – excretory pore cell; g – pharyngeal gland cell; ga – gonad arm; ph – pharynx; pv – pharyngeal-intestinal valve; oo – oocyte; r – rectum; sp – spermatheca.
Mentions: Two integrated and three extrachromosomal transgenic lines carrying tat-2::nls::gfp expression cassettes were made by particle bombardment (Figure 4A). With the exception of a few instances of ectopic transcription in the extrachromosomal lines, all five generally exhibit nearly identical patterns of reporter expression. Curiously, GFP fluorescence in the tat-2::nls::gfp transgenic nematodes emanates not from the nucleus, as would be expected with an NLS-tagged reporter, but mostly from the plasma membrane region (Figure 4B–H). Apparently, the short TAT-2-coding fragment that is retained in the tat-2 expression cassette "overpowers" the NLS and directs the chimeric reporter peptide to the plasma membrane compartment.

Bottom Line: Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system.Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant.These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania 16802, USA. lyssenn@ccf.org

ABSTRACT

Background: P-type ATPases in subfamily IV are exclusively eukaryotic transmembrane proteins that have been proposed to directly translocate the aminophospholipids phosphatidylserine and phosphatidylethanolamine from the exofacial to the cytofacial monolayer of the plasma membrane. Eukaryotic genomes contain many genes encoding members of this subfamily. At present it is unclear why there are so many genes of this kind per organism or what individual roles these genes perform in organism development.

Results: We have systematically investigated expression and developmental function of the six, tat-1 through 6, subfamily IV P-type ATPase genes encoded in the Caenorhabditis elegans genome. tat-5 is the only ubiquitously-expressed essential gene in the group. tat-6 is a poorly-transcribed recent duplicate of tat-5. tat-2 through 4 exhibit tissue-specific developmentally-regulated expression patterns. Strong expression of both tat-2 and tat-4 occurs in the intestine and certain other cells of the alimentary system. The two are also expressed in the uterus, during spermatogenesis and in the fully-formed spermatheca. tat-2 alone is expressed in the pharyngeal gland cells, the excretory system and a few cells of the developing vulva. The expression pattern of tat-3 is almost completely different from those of tat-2 and tat-4. tat-3 expression is detectable in the steroidogenic tissues: the hypodermis and the XXX cells, as well as in most cells of the pharynx (except gland), various tissues of the reproductive system (except uterus and spermatheca) and seam cells. Deletion of tat-1 through 4 individually interferes little or not at all with the regular progression of organism growth and development under normal conditions. However, tat-2 through 4 become essential for reproductive growth during sterol starvation.

Conclusion: tat-5 likely encodes a housekeeping protein that performs the proposed aminophospholipid translocase function routinely. Although individually dispensable, tat-1 through 4 seem to be at most only partly redundant. Expression patterns and the sterol deprivation hypersensitivity deletion phenotype of tat-2 through 4 suggest that these genes carry out subtle metabolic functions, such as fine-tuning sterol metabolism in digestive or steroidogenic tissues. These findings uncover an unexpectedly high degree of specialization and a widespread involvement in sterol metabolism among the genes encoding the putative aminophospholipid translocases.

Show MeSH
Related in: MedlinePlus