Previously characterized mammalian soluble guanylyl cyclases form ␣/␤ heterodimers that can be activated by the gaseous messenger, nitric oxide, and the novel guanylyl cyclase modulator YC-1. Four mammalian subunits have been cloned named ␣ 1 , ␤ 1 , ␣ 2 , and ␤ 2 . The ␣ 1 /␤ 1 and ␣ 2 /␤ 1 heterodimeric enzyme isoforms have been rigorously characterized. The role of the ␤ 2 subunit has remained elusive. Here we isolate a novel variant of this subunit and show that the ␤ 2 subunit does not need to form heterodimers for catalytic activity because enzyme activity can be measured when it is expressed alone in Sf9 cells. In analogy to the ␤ 3 subunit recently isolated from the insect Manduca sexta, activity was dependent on the presence of 4 mM free Mn 2؉ . The EC 50 values for the NO-donor diethylamine/NO were shifted to the left by 1 order of magnitude as compared with the ␣ 1 /␤ 1 heterodimeric form. In the presence of the detergent Tween, NO sensitivity of ␤ 2 was abolished, but the enzyme could be activated by protoporphyrin IX, indicating removal of a prosthetic heme group and exchange for the heme precursor. We suggest that the ␤ 2 subunit is the first mammalian NO-sensitive guanylyl cyclase lacking a heterodimeric structure.

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We have recently shown that nitric oxide activates the beta2 subunit of soluble guanylyl cyclase. In the present study, we show developmental regulation of this subunit. Analysis of mRNA expression by RT-PCR and RNase protection analysis in kidneys revealed no expression of the beta2 subunit in neonatal and strong expression in adult rats. A reciprocal regulation with much lower expression levels was observed in rat lung. Further examination of kidneys from 3, 6, 16, 22, 25, 31 and 36-day-old rats showed that significant expression appears between postnatal day 16 and 22. Isolation of the rat beta2 promoter by genome walking and cloning into a reporter gene vector showed promoter activity for the sense but not the antisense construct providing an in vitro assay for further analysis of the developmental beta2 subunit regulation.

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The connection between Pediatric Inflammatory Multisystem Syndrome (PIMS) and Kawasaki Disease (KD) is not yet fully understood. Using the same national registry, clinical features and outcome of children hospitalized in Germany, and Innsbruck (Austria) were compared. Reported to the registry were 395 PIMS and 69 KD hospitalized patients. Patient age in PIMS cases was higher than in KD cases (median 7 [IQR 4–11] vs. 3 [IQR 1–4] years). A majority of both PIMS and KD patients were male and without comorbidities. PIMS patients more frequently presented with organ dysfunction, with the gastrointestinal (80%), cardiovascular (74%), and respiratory (52%) systems being most commonly affected. By contrast, KD patients more often displayed dermatological (99% vs. 68%) and mucosal changes (94% vs. 64%), plus cervical lymph node swelling (51% vs. 34%). Intensive care admission (48% vs. 19%), pulmonary support (32% vs. 10%), and use of inotropes/vasodilators (28% vs. 3%) were higher among PIMS cases. No patients died. Upon patient discharge, potentially irreversible sequelae—mainly cardiovascular—were reported (7% PIMS vs. 12% KD). Despite differences in age distribution and disease severity, PIMS and KD cases shared many common clinical and prognostic characteristics. This supports the hypothesis that the two entities represent a syndrome continuum.