Towler, M. C. et al. A novel short splice variant of the tumour suppressor LKB1 is required for spermiogenesis. Biochem. J. 416, 1-14

Division of Molecular Physiology, School of Life Sciences, University of Dundee, Dundee, Scotland, UK.
Biochemical Journal (Impact Factor: 4.4). 10/2008; 416(1):1-14. DOI: 10.1042/BJ20081447
Source: PubMed


LKB1 was discovered as a tumour suppressor mutated in Peutz-Jeghers syndrome, and is a gene involved in cell polarity as well as an upstream protein kinase for members of the AMP-activated protein kinase family. We report that mammals express two splice variants caused by alternate usage of 3'-exons. LKB1(L) is the previously described form, while LKB1(S) is a novel form in which the last 63 residues are replaced by a unique 39-residue sequence lacking known phosphorylation (Ser(431)) and farnesylation (Cys(433)) sites. Both isoforms are widely expressed in rodent and human tissues, although LKB1(S) is particularly abundant in haploid spermatids in the testis. Male mice in which expression of Lkb1(S) is knocked out are sterile, with the number of mature spermatozoa in the epididymis being dramatically reduced, and those spermatozoa that are produced have heads with an abnormal morphology and are non-motile. These results identify a previously undetected variant of LKB1, and suggest that it has a crucial role in spermiogenesis and male fertility.

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Available from: Silvina Meroni, Mar 03, 2015
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    • "Thus, hypothermia increases AMPK phosphorylation and, hence its activity in vivo [2]. Although there are several AMPK-related protein kinases described in the germ cells of testes [46] [52] and in spermatozoa [51], only recently the functionality of AMPK has been associated with motility regulation [15] [43]. This evidence suggests that the freezing–thawing process can modify sperm AMPK activity resulting in changes in the overall function of post-thawed cells. "
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    ABSTRACT: This study evaluated the effect of the use of hypometabolic TRIS extenders in the presence or the absence of AMPK activators as well as the utilization of high cooling rates in the refrigeration step on the freezability of stallion sperm. Twelve ejaculates were cryopreserved using Botucrio® as a control extender and a basic TRIS extender (HM-0) separately supplemented with 10 mM metformin, 2 mM 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), 2 mM Adenosine monophosphate (AMP), 40 μM compound C AMPK inhibitor or 2 mM AMP + 40 μM compound C. Our results showed that the utilization of a hypometabolic TRIS extender supplemented or not with AMP or metformin significantly improves stallion sperm freezability when compared with a commercial extender. Additionally, high cooling rates do not affect stallion sperm quality after cooling and post-thawing. Finally, stallion spermatozoa present several putative AMPK sperm isoforms that do not seem to respond to classical activators, but do respond to the Compound C inhibitor.
    Cryobiology 11/2014; 69(3). DOI:10.1016/j.cryobiol.2014.10.008 · 1.59 Impact Factor
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    • "Cell lysates (100 lg protein) were immunoprecipitated by incubation at 4 °C for 2 h on a roller mixer with 6 ll of anti-AMPKa1/a2 antibody coupled to protein G-Sepharose, and the immunoprecipitates assayed for AMPK using the AMARA peptide [22]. When AMPK activity was assayed in HEK-293 cells expressing recombinant FLAG-tagged c2 subunit, immunoprecipitation was performed using 7 ll of EZview Red anti-FLAG M2 affinity gel from Sigma [18] "
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    ABSTRACT: AMPK is known to be activated by oxidative stress. Addition of glucose oxidase to cells generates H2O2 at a constant rate that is opposed by enzymic degradation, providing a good model for physiological oxidative stress. AMPK activation by glucose oxidase correlated with increases in cellular AMP:ATP and was greatly reduced in cells expressing an AMP-insensitive AMPK mutant, although a small degree of activation remained. The effects of increased AMP were partly due to inhibition of Thr172 dephosphorylation. These results suggest that changes in adenine nucleotides, rather than direct oxidative modification, are the major drivers of AMPK activation during oxidative stress.
    FEBS Letters 07/2014; 588(18). DOI:10.1016/j.febslet.2014.07.025 · 3.17 Impact Factor
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    • "Previously, some studies including knockout mice suggested a crucial role of AMPK-related kinases in spermatozoa function [17] [18]. Thus, a new shorter isoform of the AMPK upstream kinase LKB1, called LKB1s, which is expressed predominantly in haploid sperm cells from mammal testes [17], is pointed to play an essential role in spermiogenesis and fertility (motility) in mice. Additionally, the branch of AMPK in the human quinome tree includes the " serine/threonine kinase testis specific " TSSK family. "
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    ABSTRACT: Spermatozoa undergo energy- and metabolism- dependent processes to successfully fertilize the oocyte. AMP-activated protein kinase, AMPK, is a sensor of cell energy. We recently showed that AMPK controls spermatozoa motility. Our aims are i) to investigate the intracellular localization of AMPK in boar spermatozoa by immunofluorescence, ii) to study whether AMPK plays a role in other relevant processes of spermatozoa: mitochondrial membrane potential (∆Ψm), plasma membrane lipid disorganization, outward phosphatidylserine (PS) exposure, acrosome integrity and induced-acrosome reaction by flow cytometry and iii) to investigate intracellular AMPK pathways by western blot. Spermatozoa were incubated under different conditions in presence or absence of compound C (CC, 30μM), an AMPK inhibitor and/or cAMP analogue 8Br-cAMP. AMPKα protein is expressed at the entire acrosome and at the midpiece of spermatozoa flagellum, whereas phospho-Thr(172)-AMPK is specifically localized at the apical part of acrosome and at flagellum midpiece. CC treatment rapidly confers head-to-head aggregation-promoting property to spermatozoa. Long term AMPK inhibition in spermatozoa incubated in TCM significantly reduces high ∆Ψm. Moreover, AMPK inhibition significantly induces plasma membrane lipid disorganization and simultaneously reduces outward PS translocation at plasma membrane in a time-dependent manner. Acrosomal integrity in TCM is significantly enhanced when AMPK is inhibited. However, neither acrosome reaction nor membrane lipid disorganization induced by ionophore A23187 are affected by CC. AMPK phosphorylation is potently stimulated upon PKA activation in spermatozoa. This work suggests that AMPK, lying downstream of PKA, regulates at different levels mammalian spermatozoa membrane function.
    Biochimica et Biophysica Acta 06/2013; 1828(9). DOI:10.1016/j.bbamem.2013.05.026 · 4.66 Impact Factor
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