Morphology of the lingual papillae of the polar bear (Ursus maritimus).

We examined the dorsal lingual surfaces of a newborn and an old polar bears by using scanning electron microscopy. In the newborn polar bear, the filiform papilla on the lingual apex was cylindrical in shape. The connective tissue core of the filiform papillae was needle-shaped and that of the fungiform papillae was funnel-shaped. The filiform papillae on the lingual body was dome-shaped. The connective tissue core of the filiform papillae was U-shaped and that of the fungiform papillae was column-shaped. On the lingual apex and body, there could not distinguish the filiform from fungiform papillae. The connective tissue core of the filiform papilla was different from the fungiform papilla. The vallate papillae were surrounded by a groove and pad and the surface was smooth. In the old bear, the filiform papilla on the lingual apex had several pointed processes. The processes of the filiform papilla on the lingual body were larger than those of the lingual apex. The vallate papillae were surrounded by a groove and pad and the surface was rough. There are no foliate papillae.

Heterotrimeric G protein Gαs subunit attenuates PLEKHG2, a Rho family-specific guanine nucleotide exchange factor, by direct interaction.

PLEKHG2 is a Gßγ-dependent guanine nucleotide exchange factor (GEF) for the small GTPases Rac and Cdc42, and has been shown to mediate signalling pathways such as actin cytoskeleton reorganization and serum response element (SRE)-dependent gene transcription. Here we show that the constitutively active mutant of the Gαs subunit significantly attenuated PLEKHG2-induced SRE-mediated gene transcription. Strikingly, we observed that the constitutive activation of endogenous Gαs by treatment with CTx caused a similar inhibitory effect on PLEKHG2-induced activation of SRE. However, both the enforced expression of the catalytic subunit ß of protein kinase A and the treatment with dibutyl-cyclic AMP failed to mimic the inhibitory effect of Gαs on PLEKHG2. Furthermore, the dominant negative mutant of protein kinase A had no effect on PLEKHG2-mediated SRE activation. Performing immunoprecipitation and an in vitro pulldown assay, we found that PLEKHG2 directly interacted with the active form of the Gαs subunit in cells. The interaction between PLEKHG2 and Gαs required the N-terminal region of PLEKHG2, which includes the DH domain, a functional domain of GEF, suggesting that Gαs directly masks the DH domain of PLEKHG2. In a previous study, we reported that Gßγ accelerates PLEKHG2-mediated SRE-dependent gene transcription. Interestingly, Gαs also inhibited the hyperactivation of SRE induced by the co-expression of Gßγ and PLEKHG2; however, Gαs and Gßγ bind to different regions of PLEKHG2. This is the first report to show that PLEKHG2 is a novel effector of Gαs, and is negatively regulated by the Gαs subunit through direct interaction.

Four-and-a-half LIM Domains 1 (FHL1) Protein Interacts with the Rho Guanine Nucleotide Exchange Factor PLEKHG2/FLJ00018 and Regulates Cell Morphogenesis.

PLEKHG2/FLJ00018 is a Gßγ-dependent guanine nucleotide exchange factor for the small GTPases Rac and Cdc42 and has been shown to mediate the signaling pathways leading to actin cytoskeleton reorganization. Here we showed that the zinc finger domain-containing protein four-and-a-half LIM domains 1 (FHL1) acts as a novel interaction partner of PLEKHG2 by the yeast two-hybrid system. Among the isoforms of FHL1 (i.e. FHL1A, FHL1B, and FHL1C), FHL1A and FHL1B interacted with PLEKHG2. We found that there was an FHL1-binding region at amino acids 58-150 of PLEKHG2. The overexpression of FHL1A but not FHL1B enhanced the PLEKHG2-induced serum response element-dependent gene transcription. The co-expression of FHL1A and Gßγ synergistically enhanced the PLEKHG2-induced serum response element-dependent gene transcription. Increased transcription activity was decreased by FHL1A knock-out with the CRISPR/Cas9 system. Compared with PLEKHG2-expressing cells, the number and length of finger-like protrusions were increased in PLEKHG2-, Gßγ-, and FHL1A-expressing cells. Our results provide evidence that FHL1A interacts with PLEKHG2 and regulates cell morphological change through the activity of PLEKHG2.

Morphology of the lingual papillae of the Asian short-clawed otter.

We examined the dorsal lingual surface of an adult Asian short-clawed otter (Aonyx cinerea) by using scanning electron microscopy. The filiform papilla on the lingual apex had some pointed processes. The connective tissue core of the filiform papillae consisted of several rod-like processes, and the connective tissue core with a long process was rarely observed. The filiform papilla on the lingual body had several pointed processes and the fungiform papilla had smooth surface. The connective tissue core of the filiform papillae consisted of a large main and several small processes. The vallate papillae were surrounded by a groove and some pads, and many processes were observed on this surface. The tongue of the Asian short-clawed otter was different from that of the Japanese marten belong to family Mustelidae.

Morphology of the lingual papillae of the black-backed jackal (Canis mesomelas).

We examined the dorsal lingual surface of an adult black-backed jackal (Canis mesomelas) by using scanning electron microscopy. The filiform papilla on the lingual apex exhibited a crown-like shape with several pointed processes. The connective tissue core of the filiform papilla was U-shaped. The filiform papillae on the lingual body had several pointed processes. The connective tissue core of the filiform papillae consisted of one large and several small conical papillae. The fungiform papillae on the lingual apex and body had a smooth surface. The connective tissue core of the fungiform papillae was not hollow and did not have processes. The vallate papillae were surrounded by a groove and pad with many processes on the surface. The connective tissue core of the vallate papillae had many ditches. Thus, the tongue of the black-backed jackal more closely resembles that of the bush dog than those of the raccoon dog or fox.