TY - JOUR
T1 - Reevaluation of the role of LIP-1 as an ERK/MPK-1 dual specificity phosphatase in the C. elegans germline
AU - Das, Debabrata
AU - Seemann, Jacob
AU - Greenstein, David
AU - Schedl, Tim
AU - Arur, Swathi
N1 - Funding Information:
ACKNOWLEDGMENTS. We thank N. Silva, Y. Kim, and V. Jantsch for providing the SYP-1, HTP-3, and p-SUN-1(S8) antibodies, respectively. We thank members of the S.A. laboratory for critical discussions during the study. Research reported in this publication was supported by the National Institute of General Medical Sciences of the NIH under Award R01 GM98200 and National Institute of Child Health and Development of the NIH under Award R01 HD101269 from the S.A. laboratory. D.D. is funded through the Odyssey Postdoctoral Fellowship (supported by the Kimberly-Clark Foundation) and MD Anderson Cancer Center. S.A. is an Andrew Sabin Family Foundation Fellow. D.G. is funded by GM57173 from the NIH. T.S. is funded by R01 GM100756. Some strains were provided by the Caenorhabditis Genetics Center (CGC), which is funded by the NIH Office of Research Infrastructure Programs (P40 OD010440).
Publisher Copyright:
© 2022 National Academy of Sciences. All rights reserved.
PY - 2022/1/18
Y1 - 2022/1/18
N2 - The fidelity of a signaling pathway depends on its tight regulation in space and time. Extracellular signal-regulated kinase (ERK) controls wide-ranging cellular processes to promote organismal development and tissue homeostasis. ERK activation depends on a reversible dual phosphorylation on the TEY motif in its active site by ERK kinase (MEK) and dephosphorylation by DUSPs (dual specificity phosphatases). LIP-1, a DUSP6/7 homolog, was proposed to function as an ERK (MPK-1) DUSP in the Caenorhabditis elegans germline primarily because of its phenotype, which morphologically mimics that of a RAS/let-60 gain-of-function mutant (i.e., small oocyte phenotype). Our investigations, however, reveal that loss of lip-1 does not lead to an increase in MPK-1 activity in vivo. Instead, we show that loss of lip-1 leads to 1) a decrease in MPK-1 phosphorylation, 2) lower MPK-1 substrate phosphorylation, 3) phenocopy of mpk-1 reduction-of-function (rather than gain-of-function) allele, and 4) a failure to rescue mpk-1-dependent germline or fertility defects. Moreover, using diverse genetic mutants, we show that the small oocyte phenotype does not correlate with increased ectopic MPK-1 activity and that ectopic increase in MPK-1 phosphorylation does not necessarily result in a small oocyte phenotype. Together, these data demonstrate that LIP-1 does not function as an MPK-1 DUSP in the C. elegans germline. Our results caution against overinterpretation of the mechanistic underpinnings of orthologous phenotypes, since they may be a result of independent mechanisms, and provide a framework for characterizing the distinct molecular targets through which LIP-1 may mediate its several germline functions.
AB - The fidelity of a signaling pathway depends on its tight regulation in space and time. Extracellular signal-regulated kinase (ERK) controls wide-ranging cellular processes to promote organismal development and tissue homeostasis. ERK activation depends on a reversible dual phosphorylation on the TEY motif in its active site by ERK kinase (MEK) and dephosphorylation by DUSPs (dual specificity phosphatases). LIP-1, a DUSP6/7 homolog, was proposed to function as an ERK (MPK-1) DUSP in the Caenorhabditis elegans germline primarily because of its phenotype, which morphologically mimics that of a RAS/let-60 gain-of-function mutant (i.e., small oocyte phenotype). Our investigations, however, reveal that loss of lip-1 does not lead to an increase in MPK-1 activity in vivo. Instead, we show that loss of lip-1 leads to 1) a decrease in MPK-1 phosphorylation, 2) lower MPK-1 substrate phosphorylation, 3) phenocopy of mpk-1 reduction-of-function (rather than gain-of-function) allele, and 4) a failure to rescue mpk-1-dependent germline or fertility defects. Moreover, using diverse genetic mutants, we show that the small oocyte phenotype does not correlate with increased ectopic MPK-1 activity and that ectopic increase in MPK-1 phosphorylation does not necessarily result in a small oocyte phenotype. Together, these data demonstrate that LIP-1 does not function as an MPK-1 DUSP in the C. elegans germline. Our results caution against overinterpretation of the mechanistic underpinnings of orthologous phenotypes, since they may be a result of independent mechanisms, and provide a framework for characterizing the distinct molecular targets through which LIP-1 may mediate its several germline functions.
KW - C. elegans
KW - Germline
KW - LIP-1 DUSP
KW - MPK-1 ERK
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U2 - 10.1073/pnas.2113649119
DO - 10.1073/pnas.2113649119
M3 - Article
C2 - 35022236
AN - SCOPUS:85122848655
SN - 0027-8424
VL - 119
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 3
M1 - e2113649119
ER -