PubMed · 2582341
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J R Poley. 1985. Practical approaches to assessing liver function.. https://doi.org/10.3928/0090-4481-19850601-05
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Marine picocyanobacteria of the genera Prochlorococcus and Synechococcus, the two most abundant phototrophs on Earth, thrive in oligotrophic oceanic regions. While it is well known that specific lineages are exquisitely adapted to prevailing in situ light and temperature regimes, much less is known of the molecular machinery required to facilitate occupancy of these low-nutrient environments. Here, we describe a hitherto unknown alkaline phosphatase, Psip1, that has a substantially higher affinity for phosphomonoesters than other well-known phosphatases like PhoA, PhoX, or PhoD and is restricted to clade III Synechococcus and a subset of high light I-adapted Prochlorococcus strains, suggesting niche specificity. We demonstrate that Psip1 has undergone convergent evolution with PhoX, requiring both iron and calcium for activity and likely possessing identical key residues around the active site, despite generally very low sequence homology. Interrogation of metagenomes and transcriptomes from TARA oceans and an Atlantic Meridional transect shows that psip1 is abundant and highly expressed in picocyanobacterial populations from the Mediterranean Sea and north Atlantic gyre, regions well recognized to be phosphorus (P)-deplete. Together, this identifies psip1 as an important oligotrophy-specific gene for P recycling in these organisms. Furthermore, psip1 is not restricted to picocyanobacteria and is abundant and highly transcribed in some α-proteobacteria and eukaryotic algae, suggesting that such a high-affinity phosphatase is important across the microbial taxonomic world to occupy low-P environments.
Permanent human osteosarcoma cell lines are important tools for the study of bone cancer. As representative of an osteoblastic phenotype, they partly reflect their normal osteoblastic counterparts and, thus, may represent appropriate models to investigate the mechanisms involved in bone remodelling and in haematopoietic differentiation. In the present work, we describe a new human cell line, CAL 72, obtained from an osteosarcoma of the knee of a 10-year-old boy. These cells grow in continuous culture, and karyotypic analysis has revealed clonal abnormalities in number and structure, especially loss of chromosome Y. These cells exhibit morphological, immuno-histochemical and molecular characteristics of the osteoblastic lineage. Using RT-PCR, we have shown that the CAL 72 cell line expresses high levels of mRNA coding for several cytokines, such as G-CSF, GM-CSF, IL-1beta and IL-6. In view of this expression profile, the CAL 72 phenotype appears to be closer to normal primary osteoblasts than other reported osteosarcomas. Moreover, these cells express mRNA for both HGF and its receptor c-MET, suggesting that this autocrine loop might contribute to the invasiveness of the tumour from which CAL 72 originated.
The transferrin receptor contains a highly conserved Arg-Gly-Asp (RGD) sequence in the C-terminal region where transferrin is thought to bind. RGD sequences are commonly involved in cell adhesion. This sequence is crucial for transferrin binding, suggesting possible evolutionary links between molecules mediating iron uptake and cell adhesion.