Intramitochondrial recruitment of endolysosomes mediates Smac degradation and constitutes a novel intrinsic apoptosis antagonizing function of XIAP E3 ligase.

Intrinsic apoptosis involves BH3-only protein activation of Bax/Bak-mediated mitochondrial outer membrane permeabilization (MOMP). Consequently, cytochrome c is released from the mitochondria to activate caspases, and Smac (second mitochondria-derived activator of caspases) to inhibit XIAP-mediated caspase suppression. Dysfunctional mitochondria can be targeted for lysosomal degradation via autophagy (mitophagy), or directly through mitochondria-derived vesicle transport. However, the extent of autophagy and lysosomal interactions with apoptotic mitochondria remains largely unknown. We describe here a novel pathway of endolysosomal processing of mitochondria, activated in response to canonical BH3-only proteins and mitochondrial depolarization. We report that expression of canonical BH3-only proteins, tBid, BimEL, Bik, Bad, and mitophagy receptor mutants of atypical BH3-only proteins, Bnip3 and Bnip3L/Nix, leads to prominent relocalization of endolysosomes into inner mitochondrial compartments, in a manner independent of mitophagy. As an upstream regulator, we identified the XIAP E3 ligase. In response to mitochondrial depolarization, XIAP actuates Bax-mediated MOMP, even in the absence of BH3-only protein signaling. Subsequently, in an E3 ligase-dependent manner, XIAP rapidly localizes inside all the mitochondria, and XIAP-mediated mitochondrial ubiquitylation catalyses interactions of Rab membrane targeting components Rabex-5 and Rep-1 (RFP-tagged Rab escort protein-1), and Rab5- and Rab7-positive endolysosomes, at and within mitochondrial membrane compartments. While XIAP-mediated MOMP permits delayed cytochrome c release, within the mitochondria XIAP selectively signals lysosome- and proteasome-associated degradation of its inhibitor Smac. These findings suggest a general mechanism to lower the mitochondrial apoptotic potential via intramitochondrial degradation of Smac.

Response to myocardial ischemia/reperfusion injury involves Bnip3 and autophagy.

Ischemia and reperfusion (I/R) injury is associated with extensive loss of cardiac myocytes. Bnip3 is a mitochondrial pro-apoptotic Bcl-2 protein which is expressed in the adult myocardium. To investigate if Bnip3 plays a role in I/R injury, we generated a TAT-fusion protein encoding the carboxyl terminal transmembrane deletion mutant of Bnip3 (TAT-Bnip3DeltaTM) which has been shown to act as a dominant negative to block Bnip3-induced cell death. Perfusion with TAT-Bnip3DeltaTM conferred protection against I/R injury, improved cardiac function, and protected mitochondrial integrity. Moreover, Bnip3 induced extensive fragmentation of the mitochondrial network and increased autophagy in HL-1 myocytes. 3D rendering of confocal images revealed fragmented mitochondria inside autophagosomes. Enhancement of autophagy by ATG5 protected against Bnip3-mediated cell death, whereas inhibition of autophagy by ATG5K130R enhanced cell death. These results suggest that Bnip3 contributes to I/R injury which triggers a protective stress response with upregulation of autophagy and removal of damaged mitochondria.

Factors influencing single mother's employment status.

Changes in the welfare system limit the length of time a person can receive welfare benefits, thus mandating employment for many current welfare recipients. Single mothers with young children who do not become employed will lose financial support for housing, food, clothing, and health care and place their own and their children's health and safety at risk. The purpose of this qualitative study was to explore women's experiences of being unemployed and to examine the barriers to employment perceived by single mothers who expressed a desire to be employed. Nine mothers were recruited from a larger sample of single mothers who had participated in a quantitative study about employment conducted 1 to 2 years earlier. Using focus group interviews, mothers were asked what it was like to be a single mother, and then what barriers to their employment they perceived. Two dimensions were identified from the mothers' statements. The first, a sense of obligation, included themes of "being there" for their own and their child's benefit and doing what it takes to optimize the child's growth and development. The second, negotiating the obstacles, referred to problems regarding child care, lack of involvement of the child's father and lack of support from relatives and friends for the mother's efforts toward securing employment. These findings have important implications for welfare reform, namely, that efforts aimed at moving nonemployed single mothers into the workforce will fail if these factors are not considered.

Catch-up head growth and motor performance in very-low-birthweight infants.

The relationship between catch-up head growth and motor performance was examined in 48 very-low-birthweight (< 1,500 g) infants. All infants were nonasphyxiated, normocephalic, and appropriately grown for gestational age at birth. Serial cranial ultrasonography during the first month of life revealed no intracranial pathology. The age of catch-up head growth, defined as the corrected age when the head circumference recovered to the 5th percentile, was determined for each infant. At 12 months corrected age, the infants were evaluated and grouped according to normal (n = 37) or abnormal (n = 11) motor assessments. The abnormal group achieved catch-up head growth by 7.7 +/- 2.1 months vs 3.7 +/- 3.1 months for the normal group (P < .05). Only 27% of the motor-delayed infants achieved catch-up head growth by 6 months corrected age, as compared with 89% of the normal infants (P < .05). Premature infants who have achieved catch-up head growth by 6 months corrected age, corresponding to the period of maximal postnatal brain growth, have fewer motor abnormalities than infants who attain catch-up head growth later. There is a significant relationship between head circumference at 6 months corrected age and motor development in very-low-birthweight infants.

The effect of abdominal incisions on early motor development of infants with necrotizing enterocolitis.

Eighteen very low-birthweight infants with necrotizing enterocolitis (NEC) underwent periodic neurodevelopmental testing until two years of age. They were grouped according to whether they had had surgical intervention (N = 6) or non-surgical therapy (N = 12). At eight and 15 months corrected age, a significantly greater number of the surgical group exhibited motor delay. At 24 months, only one infant in the surgical group had persistent motor delays. These findings indicate a higher incidence of motor delays in infants requiring surgery for NEC. The delays involved skills influenced by the abdominal musculature. These motor delays persisted up to 24 months, but appeared to resolve with time.