Basement membrane structures, or their main component, type IV collagen, have been detected in all multicellular animal species, except sponges. We cancel this exception by the demonstration of type IV collagenous sequences in a new marine sponge species by cDNA and genomic DNA studies. One of these sequences is long enough to demonstrate the specific characteristics of type IV collagen chains. The 12 cysteines are at conserved positions in the carboxyl-terminal non-helical NCl domain, as are the interruptions in the carboxyl-terminal end of the triple helical domain. The gene organization of the region coding for the NCl domain is similar to that of the human genes COL4A2, COL4A4 and COL4A6. An additional, shorter sequence suggests the presence of a second chain. The expected tissue localization of this collagen has been confirmed using polyclonal antibodies raised against a sponge recombinant protein. These results demonstrate that type IV collagen is representated in all animal phyla. It is actually the only known ubiquitous collagen and it has at least two different alpha chains in all the species where it has been characterized.
Polo-like kinase 1 (PLK1) plays key roles in the regulation of mitotic progression, including mitotic entry, spindle formation, chromosome segregation, and cytokinesis.
To determine the subunit composition of high-affinity kainate receptors in native neurons is a challenging problem because of the expression of more than one GluR subunit. In the present study the question of whether GluR5 and/or GluR6 subunits combine with KA-1 or KA-2 subunits in vivo is addressed by performing detailed physiological, pharmacological, and molecular characterization of functional kainate receptor channels in acutely dissociated trigeminal ganglion (TG) neurons. The results show that (1) smaller diameter TG neurons (Ͻ30 m) respond to L-glutamate and kainate, and the currents gated by kainate desensitize with prolonged agonist exposure; (2) all kainate receptor subunits are detected to some extent by reverse transcriptase-PCR, whereas glutamate receptor subunits GluR5 and KA-2 are expressed at high levels in the TG; (3) there is an obvious similarity between the features of native kainate receptor channels in TG neurons and of heteromeric recombinant GluR5(R)/KA-2 channels in pharmacological properties, desensitization, rectification, ion permeability, and mean channel conductance; and (4) the age-dependent increase in GluR5 and KA-2 RNA levels in the TG is correlated well with an increased number of kainate-sensitive cells during postnatal development. Our data suggest that the heteromeric GluR5/ KA2 combination actually occurs in TG neurons and give a clue as to the subunit composition of native kainate receptor channels.
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