MUC4 involvement in ErbB2/ErbB3 phosphorylation and signaling in response to airway cell mechanical injury

The receptor tyrosine kinases ErbB2 and ErbB3 are phosphorylated in response to injury of the airway epithelium. Since we have shown that the membrane mucin MUC4 can act as a ligand/modulator for ErbB2, affecting its localization in polarized epithelial cells and its phosphorylation, we questioned whether Muc4 was involved, along with ErbB2 and ErbB3, in the damage response of airway epithelia. To test this hypothesis, we first examined the localization of MUC4 in human airway samples. Both immunocytochemistry and immunofluorescence showed a co‐localization of MUC4 and ErbB2 at the airway luminal surface. Sequential immunoprecipitation and immunoblotting from airway cells demonstrated that the MUC4 and ErbB2 are present as a complex in airway epithelial cells. To assess the participation of MUC4 in the damage response, cultures of NCI‐H292 or airway cells were scratch‐wounded, then analyzed for association of phospho‐ErbB2 and ‐ErbB3 with MUC4 by sequential immunoprecipitation and immunoblotting. Wounded cultures exhibited increased phosphorylation of both receptors in complex with MUC4. Scratch wounding also increased activation of the downstream pathway through Akt, as predicted from our previous studies on Muc4 effects on ErbB2 and ErbB3. The participation of MUC4 in the phosphorylation response was also indicated by siRNA repression of MUC4 expression, which resulted in diminution of the phosphorylation of ErbB2 and ErbB3. These studies provide a new model for the airway epithelial damage response, in which the MUC4–ErbB2 complex is a key element in the sensor mechanism and phosphorylation of the receptors. J. Cell. Biochem. 107: 112–122, 2009. © 2009 Wiley‐Liss, Inc.     

Rat liver mitochondria contain two immunologically distinct dihydrolipoamide dehydrogenases

We have raised antisera against dihydrolipoamide dehydrogenase. One antigen was isolated from purified bovine kidney pyruvate dehydrogenase complex (PDC). The other antigen was a commercial preparation of porcine heart dihydrolipoamide dehydrogenase (E3) which did not first involve purification of the alpha-keto acid dehydrogenase complex(es). Both antibody preparations cross-reacted with the E3 components of PDC, alpha-ketoglutarate dehydrogenase complex, and branched-chain keto acid dehydrogenase complex. This demonstrates the immunological identity of the E3 components. These sera totally precipitated E3 activity from the purified complexes, from purified preparations of E3, and from extracts of rat heart and kidney mitochondria. The two sera vary in their reaction with rat liver mitochondrial extracts: the anti PDC-E3 serum left residual E3 activity (approximately 50% of the original) that was precipitable by the anti-E3 anti-serum. This indicates that liver contains two immunologically distinct forms of E3. Metabolic assays measuring the differential effects of the two sera on the glycine decarboxylation reaction suggest that the form which is immunologically nonreactive with the anti-PDC-E3 serum could represent the E3 involved in the glycine cleavage system.     

A family with RP3 type of X-linked retinitis pigmentosa: an association with ciliary abnormalities

Summary The results of linkage analysis in a family with X-linked retinitis pigmentosa (XLRP) are presented. Probe M27B (DXS255), localised to Xp11.22, was only loosely linked to XLRP, whereas pHOC3 (OTC), in the more distal Xp21.1 region, was tightly linked. In this family, the conditional probability of an RP3 locus (in Xp21.1–p11.4) was found to be 0.978 compared with 0.021 for an RP2 locus (in Xp11.4–p11.2). Risk assessment showed that 2 out of 4 at risk females showing no clinical abnormality have a high probability of being genetic carriers of XLRP. Some affected males have recurrent respiratory infections as a result of a condition indistinguishable from the immotile cilia syndrome; indeed, there is an association between XLRP and susceptibility to respiratory infections in the majority of affected males. The possibility that previously observed ciliary abnormalities in XLRP patients might be associated specifically with an RP3 locus abnormality is discussed.     

Genetic Analysis of a Kindred With X-linked Mental Handicap and Retinitis Pigmentosa

A kindred is described in which X-linked nonspecific mental handicap segregates together with retinitis pigmentosa. Carrier females are mentally normal but may show signs of the X-linked retinitis pigmentosa carrier state and become symptomatic in their later years. Analysis of polymorphic DNA markers at nine loci on the short arm of the X chromosome shows that no crossing-over occurs between the disease and Xp11 markers DXS255, TIMP, DXS426, MAOA, and DXS228. The 90% confidence limits show that the locus is in the Xp21-q21 region. Haplotype analysis is consistent with the causal gene being located proximal to the Xp21 loci DXS538 and 5'-dystrophin on the short arm of the X chromosome. The posterior probability of linkage to the RP2 region of the X chromosome short arm (Xp11.4-p11.23) is .727, suggesting the possibility of a contiguous-gene-deletion syndrome. No cytogenetic abnormality has been identified.     

An aetiological study of 290 XXY males,with special reference to the role of paternal age

Summary Data on 290 non-mosaic 47,XXY males have been analysed for possible associations with parental ages at birth, season of birth, sex ratio among sibs, and twinning. Comparison with matched population controls revealed a highly significant association with parental age, which was fully explained by dependence on maternal age and maternal age alone. The maternal age effect was determined with greater precision than in an earlier study of the same material, in which siblings were used as controls, and was estimated to result in an increased risk of between 5% and 10% per annum (p.a.). The estimated independent effect of paternal age, after fitting maternal age, was marginally (but not significantly) negative, and excluded an increased risk in excess of 3% p.a. Paternal age therefore appears to have little if any independent significance in the aetiology of 47,XXY. After correcting for seasonal variations in the population birth rate and smoothing, there was a peak of XXY births in March and a trough in November. Though not statistically significant, the pattern resembled that reported in previous studies, and was similar for both younger and older mothers. The twinning rate for both the XXYs and their sibs, and the sex ratio among the latter, were close to the corresponding population values.     

Effects of trophic morphology and behavior on foraging rates of three Hawaiian honeycreepers

Summary The effects of trophic morphology and behavior of three Hawaiian honeycreepers (Fringillidae: Drepanidinae) upon their foraging rates on the flowers of Vaccinium calycinum are examined. The Maui Creeper (Paroreomyza montana), the Amakihi (Hemianathus virens), and the I'iwi (Vestiaria coccinea) show shifts from a short straight bill to a long decurved bill, from a tongue adapted for insect feeding to one specialized for nectar, and diets ranging from primarily probing for insects to primarily nectarivorous. This diversity is examined feeding on the simple straight tubular corollas of the Vaccinium. Significant differences (P<0.001, t-tests) exist among the birds with respect to foraging rates on these flowers. The I'iwi, with its greatly decurved (64°) bill feeds the quickest (2.09 s/flower) while the Maui Creeper with its rather straight (18°) bill feeds the slowest (3.87 s/flower). These differences are seen to be the result of differing abilities of tongues to extract nectar as well as differing behavioral tactics of floral exploration and nectar extraction. This suggests that predictions of foraging efficiency based solely on bill morphology are not necessarily valid, and that other factors (tongue morphology, foraging maneuvers, and typical food spectrum) must also be considered.     

Membrane-microfilament interactions in ascites tumor cell microvilli. Identification and isolation of a large microfilament-associated membrane glycoprotein complex

[14C]Glucosamine metabolic labeling and concanavalin A blots were used to identify four major glycoprotein species associated with ascites tumor cell microvillar microfilament cores and with a transmembrane complex containing actin. Phalloidin shift analysis of glucosamine-labeled microvilli showed that glycoproteins of 110-120, 80, 65, and 55 kDa are stably associated with the microfilament cores. Analysis of large (greater than 10(6) kDa) transmembrane complexes from microvillar membranes made under microfilament-depolymerizing conditions (Carraway, C. A. C., Jung, G., and Carraway, K. L. (1983) Proc. Natl. Acad. Sci. U. S. A. 80, 430-434) revealed glycoproteins of the same Mr values, showing the same relative staining or labeling patterns as those observed with the microfilament cores. Gel filtration of high salt, high pH extracts of intact microvilli, microfilament cores, or transmembrane complexes showed that in all of these fractions the glycoproteins are associated in a very large, stable complex. The glycoprotein multimer was isolated essentially free of actin and other components by Sephacryl S-1000 chromatography of microvilli, microvillar membranes prepared at pH 11, microfilament cores, or transmembrane complex fractions in Triton X-100, 1 M KCl, glycine, pH 9.5. Purified glycoprotein complex bound actin when incubated under polymerizing conditions. The presence of the glycoprotein heteromultimer in both microfilament cores and transmembrane complex from isolated membranes and the association of the purified glycoprotein complex with actin are consistent with our hypothesis that the glycoprotein-containing transmembrane complex is an association site for microfilaments at the plasma membrane.