Glycolytic enzymes localize to ribonucleoprotein granules in Drosophila germ cells, bind Tudor and protect from transposable elements

Abstract

Germ cells give rise to all cell lineages in the next-generation and are responsible for the continuity of life. In a variety of organisms, germ cells and stem cells contain large ribonucleoprotein granules. Although these particles were discovered more than 100 years ago, their assembly and functions are not well understood. Here we report that glycolytic enzymes are components of these granules in Drosophila germ cells and both their mRNAs and the enzymes themselves are enriched in germ cells. We show that these enzymes are specifically required for germ cell development and that they protect their genomes from transposable elements, providing the first link between metabolism and transposon silencing. We further demonstrate that in the granules, glycolytic enzymes associate with the evolutionarily conserved Tudor protein. Our biochemical and single-particle EM structural analyses of purified Tudor show a flexible molecule and suggest a mechanism for the recruitment of glycolytic enzymes to the granules. Our data indicate that germ cells, similarly to stem cells and tumor cells, might prefer to produce energy through the glycolytic pathway, thus linking a particular metabolism to pluripotency.

An in vivo proteomic analysis of the Me31B interactome in Drosophila germ granules

“…Four glycolytic enzymes, pyruvate kinase (PyK), enolase (Eno), 6-phosphofructokinase (PfK), and phosphoglycerate kinase (PgK), were identified in the Me31B complexes. In accordance with our data, PyK and PgK were found in polar granules by immuno-EM [22]. Furthermore, PyK and Eno are both found in Tud and Aub complexes [23], and PyK directly binds to Tud and contains sDMA [22].…”

“…In accordance with our data, PyK and PgK were found in polar granules by immuno-EM [22]. Furthermore, PyK and Eno are both found in Tud and Aub complexes [23], and PyK directly binds to Tud and contains sDMA [22]. Considering that Me31B may bind to Tud in a similar way (see below), we propose a model where the glycolytic enzymes are linked to Me31B via scaffold protein Tud (Fig.…”

“…These synthesized peptides originate from the N‐terminal sequence of Aub and contain multiple sDMAs (see Materials and methods). When bound by an excessive amount of the peptides, Tud loses binding to other sDMA‐containing proteins . The results showed that, compared to the nontreated HA‐Tud, the sDMA peptide‐quenched HA‐Tud bound significantly less on the Me31B‐GFP beads.…”

Germ Plasm Biogenesis—An Oskar-Centric Perspective

“…Another example is Pyruvate kinase (Pyk), which contains sDMAs modification, localizes to polar granules and interacts with Tudor (Thomson et al, 2008). Interestingly, not only Pyk but several enzymes in the glycolytic pathway localize specifically to the germ plasm and affect germ cell formation (Gao et al, 2015). It has therefore been suggested that Tudor may recruit glycolytic enzymes to the germ plasm to provide a local source of ATP for helicases like Vasa.…”

An unregulated regulator: Vasa expression in the development of somatic cells and in tumorigenesis

“…Further, knockdown of Enolase or Pyruvate Kinase resulted in reduction of piRNAs, and compromised germ cell formation. Through the interaction with germ line factors, therefore, glycolytic pathway components appear to function in protecting the genome from transposable elements and in germ cell formation (Gao et al, 2015). Since Tudor and Vasa are reported to function together in the germ cells (Arkov et al, 2006), it will be intriguing to test if Vasa is involved in this process of metabolic pathway.…”