[Assessment of disease activity of rheumatoid arthritis by ultrasonography].

Rheumatoid arthritis (RA) is a typical autoimmune disease of connective tissue, with the synovial joints as the main site of the disease. Bone erosion occurs in the initial stage. A key factor in treating and understanding the prognosis of the disease is to determine which stage of the lesion is caused by rheumatoid arthritis. In order to assess bone erosion and determine the degree of synovial proliferation, ultrasonography has come into the spotlight as a method of visualizing the rheumatoid arthritis lesion, which cannot be distinguished superficially from the cutaneous condition. Joint ultrasonography is a relatively inexpensive procedure that can be used to examine patients repeatedly; therefore, we can compare serial data from such patients. The joint lesion, which we focused on, can be understood in real time and is superior in many respects. However, at present, there are problems with examiner bias and the lack of a standard assessment method, because joint ultrasonography alone does not provide objective imaging findings. Now, joint ultrasonography is also useful as a supportive method to clarify mobility around the articular region. Ultrasonography might be used as a supportive method for the early diagnosis, assessment of disease activity, evaluation of the drug efficacy, prognosis, and as part of the differential diagnosis.

Importance of autophosphorylation at Ser186 in the A-loop of salt inducible kinase 1 for its sustained kinase activity.

Autophosphorylation is an important mechanism by which protein kinases regulate their own biological activities. Salt inducible kinase 1 (SIK1) is a regulator in the feedback cascades of cAMP-mediated gene expression, while its kinase domain also features autophosphorylation activity. We provide evidence that Ser186 in the activation loop is the site of autophosphorylation and essential for the kinase activity. Ser186 is located at the +4 position of the critical Thr residue Thr182, which is phosphorylated by upstream kinases such as LKB1. The relationship between phosphorylation at Ser186 and at Thr182 in COS-7 cells indicates that the former is a prerequisite for the latter. Glycogen synthase kinase-3beta (GSK-3beta) phosphorylates Ser/Thr residues located at the fourth position ahead of the pre-phosphorylated Ser/Thr residues, and inhibitors of GSK-3beta reduce the phosphorylation at Thr182. The results of an in vitro reconstitution assay also indicate that GSK-3beta could be the SIK1 kinase. However, overexpression and knockdown of GSK-3beta in LKB1-defective HeLa cells suggests that GSK-3beta alone may not be able to phosphorylate or activate SIK1, indicating that LKB1 may play a crucial role by phosphorylating SIK1 at Thr182, possibly as an initiator of the autophosphorylation cascade, and GSK-3beta may phosphorylate SIK1 at Thr182 by recognizing the priming-autophosphorylation at Ser186 in cultured cells. This may also be the case for the other isoform SIK2, but not for SIK3.

[Effect of aging on preoperative oxidative stress].

We investigated the effect of aging on preoperative oxidative stress by measuring serum hydroperoxide values in 35 patients who underwent elective surgery under general anesthesia. A small amount of blood was withdrawn through an intravenous catheter and serum hydroperoxide values were measured using the Free Radical Analytic System (FRAS4). Aging and oxidative stress are significantly and positively correlated (P < 0.001, r = 0.622). Although the reason is unknown, oxidative stress increases concomitantly with aging.

Silencing the constitutive active transcription factor CREB by the LKB1-SIK signaling cascade.

Cyclic AMP responsive element (CRE)-binding protein (CREB) is known to activate transcription when its Ser133 is phosphorylated. Two independent investigations have suggested the presence of Ser133-independent activation. One study identified a kinase, salt-inducible kinase (SIK), which repressed CREB; the other isolated a novel CREB-specific coactivator, transducer of regulated CREB activity (TORC), which upregulated CREB activity. These two opposing signals are connected by the fact that SIK phosphorylates TORC and induces its nuclear export. Because LKB1 has been reported to be an upstream kinase of SIK, we used LKB1-defective HeLa cells to further elucidate TORC-dependent CREB activation. In the absence of LKB1, SIK was unable to phosphorylate TORC, which led to constitutive activation of CRE activity. Overexpression of LKB1 in HeLa cells improved the CRE-dependent transcription in a regulated manner. The inactivation of kinase cascades by 10 nm staurosporine in LKB1-positive HEK293 cells also induced unregulated, constitutively activated, CRE activity. Treatment with staurosporine completely inhibited SIK kinase activity without any significant effect on the phosphorylation level at the LKB1-phosphorylatable site in SIK or the activity of AMPK, another target of LKB1. Constitutive activation of CREB in LKB1-defective cells or in staurosporine-treated cells was not accompanied by CREB phosphorylation at Ser133. The results suggest that LKB1 and its downstream SIK play an important role in silencing CREB activity via the phosphorylation of TORC, and such silencing may be indispensable for the regulated activation of CREB.