p24 proteins, intracellular trafficking, and behavior: Drosophila melanogaster provides insights and opportunities

Abstract

The p24 transmembrane proteins, also known as EMP24/GP25 (endomembrane protein precursor of 24kD (Schimmoller et al., 1995)) proteins, are components of coat protein (COP)-coated vesicles and are present in species as diverse as fungi, plants, flies, worms, and mammals, indicating that they have important conserved functions. Genetic, molecular, and biochemical characterization of these proteins and the loci that encode them has provided insights into their potential cellular roles, including postulated functions in vesicle cargo protein selection and sorting, COPI and COPII vesicle formation and budding, and quality control of proteins that mature through the secretory pathway. Recently, the first mutations in a Drosophila melanogaster p24 gene have been isolated and characterized. These alleles produce an interesting behavioral phenotype in females, affecting their ability to oviposit. This identification and mutant characterization of a p24 locus in Drosophila will pave the way for a better understanding of cell-type-specific functions and interactions among p24 proteins.

Drosophila melanogasterp24 genes have developmental, tissue‐specific, and sex‐specific expression patterns and functions

“…There has been very limited investigation of differential p24 mRNA isoform expression for any organism (Rötter et al, 2002;Carney and Taylor, 2003;Carney and Bowen, 2004), although alternative forms could be tissue-specifically or developmentally regulated, or they may produce different protein products. loj and CG9053 are the only Drosophila p24 genes currently expected to encode more than one transcript.…”

“…loj and CG9053 are the only Drosophila p24 genes currently expected to encode more than one transcript. Both loci are members of the gamma subclass, which consists of four genes in Drosophila (Carney and Bowen, 2004). The 5Ј-rapid amplification of cDNA ends analysis identified five alternative loj isoforms that were verified by reverse transcriptase-polymerase chain reaction (RT-PCR; Carney and Taylor, 2003).…”

“…2) and mutant phenotypes similar to loj (Bartoszewski et al, 2004), in the CNS to regulate oviposition behavior. These proteins represent three of the four p24 protein lineages (Carney and Bowen, 2004). If p24 proteins function as heterotetramers, at least in some contexts, we expect that a member of the beta group acts together with loj, eca, and bai to regulate egg-laying behavior.…”

The GOLD domain-containing protein TMED7 inhibits TLR4 signalling from the endosome upon LPS stimulation

“…Ten TMED genes are present in mammals and they are separated into four different subfamilies, α, β, δ and γ 12 . TMED proteins are highly conserved in eukaryotes 13 and exist as monomers, dimers, oligomers and hetero-oligomers 14,15 . They possess a GOLD domain, which is a β-strand-rich domain found in several proteins involved in Golgi dynamics, as well as intracellular protein trafficking 14,16 .…”

The GOLD Domain-containing Protein TMED1 Is Involved in Interleukin-33 Signaling*

“…These proteins are highly conserved in eukaryotes, and 10 TMED genes have been identified in mammals. They are separated into four subfamilies, ␣, ␤, ␦, and ␥ (15), and have been reported to exist as dimers, oligomers, and hetero-oligomers (16,17). TMED proteins localize to membranes of the early secretory pathway, such as the endoplasmic reticulum (ER) and Golgi (15), and possess a GOLD (Golgi dynamics) domain, which is a ␤-strand-rich domain found in several proteins involved in Golgi dynamics and intracellular protein trafficking (18).…”