Rabbit Anti-Human AS160 monoclonal antibody, clone H.964.8

STUDY QUESTION: Can RNA sequencing of human cumulus cells (CC) reveal molecular pathways involved in the physiology of reproductive aging? STUDY FINDING: Senescent but not young CC activate gene pathways associated with hypoxia and oxidative stress. WHAT IS KNOWN ALREADY: Shifts in socioeconomic norms are resulting in larger numbers of women postponing childbearing. The reproductive potential is sharply decreased with aging, and the reasons are poorly understood. Since CCs play an integral role in oocyte maturation and direct access to human oocytes is limited, we used whole transcriptome analysis of these somatic cells to gain insights into the molecular mechanisms playing a role in follicular senescence. STUDY DESIGN, SAMPLES/MATERIALS, METHODS: Twenty CC samples (from a total of 15 patients) were obtained from oocytes of either male factor or egg donor patients. RNA sequencing and bioinformatic tools were used to identify differentially expressed genes between CCs from seven aged and eight young patients (< 35 (years old) y.o. vs > 40 y.o.). Quantitative-PCR and immunoflourescent staining were used for validation. MAIN RESULTS AND THE ROLE OF CHANCE: RNA sequencing identified 11 572 genes expressed in CC of both age cohorts, 45 of which were differentially expressed. In CC collected from patients > 40 y.o., genes involved in the hypoxia stress response (NOS2, RORA and NR4A3), vasculature development (NR2F2, PTHLH), glycolysis (RALGAPA2 and TBC1D4) and cAMP turnover (PDE4D) were significantly overexpressed when compared with CC of patients younger than 35 y.o. LIMITATIONS, REASONS FOR CAUTION: This study focused almost exclusively on assessing the genetic differences in CC transcriptome between young and older women. These genetic findings were not fully correlated with embryonic development and clinical outcome. WIDER IMPLICATIONS OF THE FINDINGS: Our data provide a new hypothesis-follicular hypoxia-as the main mechanism leading to ovarian follicular senescence and suggest a link between cumulus cell aging and oocyte quality decay. If specific molecular findings of hypoxia would be confirmed also in oocytes, genetic platforms could screen CC for hypoxic damage and identify healthier oocytes. Protocols of ovarian stimulation in older patients could also be adjusted to diminish oocyte exposure time to hypoxic follicles. LARGE SCALE DATA: GEO accession number: GSE81579

Treebak JT, Taylor EB, Witczak CA, An D, Toyoda T, Koh HJ, Xie J, Feener EP, Wojtaszewski JF, Hirshman MF, Goodyear LJ. Identification of a novel phosphorylation site on TBC1D4 regulated by AMP-activated protein kinase in skeletal muscle. Am J Physiol Cell Physiol 298: C377-C385, 2010. First published November 18, 2009; doi: 10.1152/ajpcell.00297.2009.-TBC1D4 ( also known as AS160) regulates glucose transporter 4 (GLUT4) translocation and glucose uptake in adipocytes and skeletal muscle. Its mode of action involves phosphorylation of serine (S)/threonine (T) residues by upstream kinases resulting in inactivation of Rab-GTPase-activating protein (Rab-GAP) activity leading to GLUT4 mobilization. The majority of known phosphorylation sites on TBC1D4 lie within the Akt consensus motif and are phosphorylated by insulin stimulation. However, the 5'-AMP-activated protein kinase ( AMPK) and other kinases may also phosphorylate TBC1D4, and therefore we hypothesized the presence of additional phosphorylation sites. Mouse skeletal muscles were contracted or stimulated with 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR), and muscle lysates were subjected to mass spectrometry analyses resulting in identification of novel putative phosphorylation sites on TBC1D4. The surrounding amino acid sequence predicted that S711 would be recognized by AMPK. Using a phosphospecific antibody against S711, we found that AICAR and contraction increased S711 phosphorylation in mouse skeletal muscle, and this increase was abolished in muscle-specific AMPK alpha 2 kinase-dead transgenic mice. Exercise in human vastus lateralis muscle also increased TBC1D4 S711 phosphorylation. Recombinant AMPK, but not Akt1, Akt2, or PKC zeta, phosphorylated purified muscle TBC1D4 on S711 in vitro. Interestingly, S711 was also phosphorylated in response to insulin in an Akt2- and rapamycin-independent, but a wortmannin-sensitive, manner, suggesting this site is regulated by one or more additional upstream kinases. Despite increased S711 phosphorylation with AICAR, contraction, and insulin, mutation of S711 to alanine did not alter glucose uptake in response to these stimuli. S711 is a novel TBC1D4 phosphorylation site regulated by AMPK in skeletal muscle.