The c-Cbl protooncogene product is a prominent substrate of protein tyrosine kinases and is rapidly tyrosine-phosphorylated upon stimulation of a wide variety of cell-surface receptors. We have identified a novel c-Cbl-interacting protein termed CIN85 with a molecular mass of 85 kDa which shows similarity to adaptor proteins, CMS and CD2AP. CIN85 mRNA is expressed ubiquitously in normal human tissues and cancer cell lines analyzed. CIN85 was basally associated with c-Cbl. For interaction of CIN85 with c-Cbl, the second SH3 domain of CIN85 was shown to serve as a central player. The CIN85-c-Cbl association was enhanced shortly after stimulation of 293 cells with epidermal growth factor (EGF) and gradually diminished to a basal level, which correlated with a tyrosine phosphorylation level of c-Cbl. Our results suggest that CIN85 may play a specific role in the EGF receptor-mediated signaling cascade via its interaction with c-Cbl.

CIN85 is an 85-kDa adaptor protein whose functions in signaling pathways are presently unknown. Using the yeast two-hybrid screen, the B cell linker protein (BLNK) was identified as a binding partner of CIN85. Coimmunoprecipitation experiments using mammalian cells revealed that CIN85 directly bound to BLNK through its SH3 domains. Immunostaining analysis showed that CIN85 and BLNK were colocalized in the cytoplasm. These results indicate a potential role of CIN85 in the B cell receptor-mediated signaling pathway. It was also found that Crk-I, Crk-II, p130(Cas), p85-PI3K, Grb2, and Sos1 were components of CIN85 complexes. CIN85 interacted with itself through its coiled-coil region, resulting in formation of a tetramer. Both the coiled-coil region and SH3 domains of CIN85 were responsible for its subcellular localization. Our data suggest that CIN85 may serve for regulation of various signaling events through formation of its diverse complexes.

Respiratory function and arterial blood gas were examined before and after a two-month exercise program performed in a pool filled with hot spring water in 22 patients (70.9 +/- 9.1 years of age) with stable chronic obstructive pulmonary disease (12 cases of bronchial asthma and 10 cases of pulmonary emphysema) treated at our hospital between 1991 and 1994. The ratio of forced expired volume in one second to forced vital capacity (FEV1%) was significantly increased after the exercise program (P < 0.05), whereas the ratio of forced vital capacity to predicted normal value (%FVC) did not change. In addition, a tendency toward an increase in peak flow without an increase in maximum expiratory flow at 25 and 50% (V25 and V50) was observed. Although PaO2 was not increased, PaCO2 was selectively decreased by the exercise program (P < 0.05). The changes in respiratory function and arterial blood gas were considered attributable to respiratory muscle training and small airway clearance. Exercise in a pool filled with hot spring water may be useful in treating chronic obstructive pulmonary disease.

Newly developed alpha1-adrenoceptor antagonists including naftopidil are free from the "prazosin-like" side effect of orthostatic hypotension and associated symptoms. We investigated the mechanism for the differential effects of naftopidil and prazosin on the development of postural hypotension, with special attention on their selectivity for the alpha1-adrenoceptor subtype. We observed that head-up tilt caused a similar extent of drop in mean arterial pressure in control, naftopidil (1 mg/kg)- or prazosin (10 microg/kg)-treated rats; however, the tilt-induced postural hypotension was recovered within 2 min in the naftopidil-treated group, but not in the prazosin-treated group. Comparing an inhibitory effect on noradrenaline-induced contraction in the rat aorta and portal vein, we found that naftopidil was sixfold less potent in the portal vein, while prazosin showed similar potency in both tissues. Reverse transcription-polymerase chain reaction analysis showed that the expression of alpha1d-adrenoceptor mRNA predominated in the aorta, while that of alpha1b-adrenoceptor mRNA predominated in the portal vein. Using cloned rat alpha1-adrenoceptor subtypes, we found that naftopidil was selective for the alpha1d-subtype with approximately ninefold higher affinity than at the other subtypes. These results show that the pharmacological character of naftopidil, combined with the differential expression of the alpha1-adrenoceptor subtype in the artery and the vein, may partly explain the differential effect of naftopidil and prazosin on head-up tilt-induced hemodynamic responses.

No abstract