Barbara A. Hocevar

TGF-Beta Induces Fibronectin Synthesis Through a c-Jun N-terminal Kinase-Dependent, Smad4-Independent Pathway

Transforming growth factor‐β (TGF‐β) exerts its effects on cell proliferation, differentiation and migration in part through its modulation of extracellular matrix components, such as fibronectin and plasminogen activator inhibitor‐1 (PAI‐1). Although the SMAD family of proteins recently has been shown to be a key participant in TGF‐β signaling, other signaling pathways have also been shown to be activated by TGF‐β. We report here that c‐Jun N‐terminal kinase (JNK), a member of the MAP kinase family, is activated in response to TGF‐β in the human fibrosarcoma HT1080‐derived cell line BAHgpt. Stable expression of dominant‐negative forms of JNK1 and MKK4, an upstream activator of JNK, results in loss of TGF‐β‐stimulated fibronectin mRNA and protein induction, while having little effect on TGF‐β‐induced levels of PAI‐1. The human fibronectin promoter contains three CRE elements, one of which has been shown to bind a c‐Jun–ATF‐2 heterodimer. Utilizing a GAL4 fusion trans‐reporting system, we demonstrate a decrease in transactivating potential of GAL4–c‐Jun and GAL4–ATF‐2 in dominant‐negative JNK1‐ and MKK4‐expressing cells. Finally, we show that TGF‐β‐induced fibronectin synthesis is independent of Smad4. These results demonstrate that TGF‐β‐mediated fibronectin induction requires activation of JNK which in turn modulates the activity of c‐Jun and ATF‐2 in a Smad4independent manner.

The adaptor molecule Disabled-2 links the transforming growth factor β receptors to the Smad pathway

Using a genetic complementation approach we have identified disabled‐2 (Dab2), a structural homolog of the Dab1 adaptor molecule, as a critical link between the transforming growth factor β (TGFβ) receptors and the Smad family of proteins. Expression of wild‐type Dab2 in a TGFβ‐signaling mutant restores TGFβ‐mediated Smad2 phosphorylation, Smad translocation to the nucleus and Smad‐dependent transcriptional responses. TGFβ stimulation triggers a transient increase in association of Dab2 with Smad2 and Smad3, which is mediated by a direct interaction between the N‐terminal phosphotyrosine binding domain of Dab2 and the MH2 domain of Smad2. Dab2 associates with both the type I and type II TGFβ receptors in vivo, suggesting that Dab2 is part of a multiprotein signaling complex. Together, these data indicate that Dab2 is an essential component of the TGFβ signaling pathway, aiding in transmission of TGFβ signaling from the TGFβ receptors to the Smad family of transcriptional activators.

Regulation of the Wnt signaling pathway by disabled-2 (Dab2)

The adaptor molecule Disabled‐2 (Dab2) has been shown to link cell surface receptors to downstream signaling pathways. Using a small‐pool cDNA screening strategy, we identify that the N‐terminal domain of Dab2 interacts with Dishevelled‐3 (Dvl‐3), a signaling mediator of the Wnt pathway. Ectopic expression of Dab2 in NIH‐3T3 mouse fibroblasts attenuates canonical Wnt/β‐catenin‐mediated signaling, including accumulation of β‐catenin, activation of β‐catenin/T‐cell‐specific factor/lymphoid enhancer‐binding factor 1‐dependent reporter constructs, and endogenous cyclin D1 induction. Wnt stimulation leads to a time‐dependent dissociation of endogenous Dab2–Dvl‐3 and Dvl‐3–axin interactions in NIH‐3T3 cells, while Dab2 overexpression leads to maintenance of Dab2–Dvl‐3 association and subsequent loss of Dvl‐3–axin interactions. In addition, we find that Dab2 can associate with axin in vitro and stabilize axin expression in vivo. Mouse embryo fibroblasts which lack Dab2 exhibit constitutive Wnt signaling as evidenced by increased levels of nuclear β‐catenin and cyclin D1 protein levels. Based on these results, we propose that Dab2 functions as a negative regulator of canonical Wnt signaling by stabilizing the β‐catenin degradation complex, which may contribute to its proposed role as a tumor suppressor.

Mechanisms of TGF-β-Induced Cell Cycle Arrest

Mitogenic growth factors stimulate cell growth by initiating a signaling cascade leading to the activation of the cyclin-dependent kinases (cdks), phosphorylation of pRb, and subsequent entry of the cell into the S phase. Transforming growth factor-β (TGF-β) is a potent antimitogen in a wide variety of cells and is postulated to inhibit cell cycle progression by blocking the late G1 activation of the cdks, thereby preventing pRb phosphorylation and S phase entry. The loss of TGF-β sensitivity in many transformed cells coupled with recent data demonstrating a deregulation of cyclins, cdks, and cdk inhibitors in many types of cancer has attracted much attention to the molecular mechanism of TGF-β-mediated growth arrest. Despite these recent advances, further research is required to elucidate how these effects of TGF-β on the cyclins, cdks, and cdk inhibitors are linked to the TGF-β receptor complex and the Smad proteins.

Intestinal diversion (colostomy or ileostomy) in patients with severe bowel dysfunction following spinal cord injury.

BACKGROUND Spinal cord injury (SCI) affects motor and sensory nervous integrity resulting in paralysis of lower or both upper and lower extremities, as well as autonomic nervous system function resulting in neurogenic bowel. SCI leads to diminished or lost sensations of the need to defecate or inability to distinguish the presence of gas versus liquid versus solid stool in the rectal vault. Sensory loss, incomplete evacuation of stool from the rectal vault, immobility, and reduced anal sphincter tone increase the risk of fecal incontinence. Gastrointestinal symptoms are associated with depression, anxiety, and significant impairments in quality of life (QOL) in a significant portion of persons with SCI. OBJECTIVESTo compare clinical, functional, or quality of life outcomes in spinal cord injured patients with gastrointestinal symptoms managed by conservative measures versus intestinal diversion (colostomy or ileostomy).To identify complications associated with ostomy surgery in patients with bowel dysfunction and SCI. SEARCH STRATEGY A systematic review of electronic databases MEDLINE and CINAHL (from January 1960 to November 2007) was undertaken using the following key words: (1) ostomy, (2) stoma, (3) colostomy, and (4) ileostomy. Boolean features of these databases were used to combine these terms with the key word “spinal cord injuries.” Prospective and retrospective studies that directly compared clinical, functional, QOL outcomes or satisfaction among patients with intestinal diversions to patients managed by conservative means were included. RESULTS Creation of an ostomy in selected patients provides equivocal or superior QOL outcomes when compared to conservative bowel management strategies. Both colostomy and ileostomy surgery significantly reduce the amount of time required for bowel management. Patients who undergo ostomy surgery tend to be satisfied with their surgery, and a significant portion report a desire to be counseled about this option earlier. There are no clear advantages when functional, clinical, or QOL outcomes associated with colostomy are compared to those seen in SCI patients undergoing ileostomy. IMPLICATIONS FOR PRACTICEThe WOC nurse plays a pivotal role in both conservative bowel management and the decision to undergo ostomy surgery.Preoperative stoma site marking is vital for the best surgical outcome.The system best suited to an individual is based on a variety of factors including but not limited to stoma location, type of effluent, peristomal plane and contours, and the individuals capabilities and preferences.Some individuals with a sigmoid or descending colostomy may benefit from colostomy irrigation as a management method.Postoperatively, assessment of pressure points for signs of tissue breakdown, evaluation of treatment methods for existing pressure ulcers with suitable modification, and support surface assessment should be included in ongoing annual follow-up visits.

Wound, Ostomy, and Continence/Enterostomal Therapy (WOC/ET) Nursing

The specialty of enterostomal therapy nursing (ET), now known as wound, ostomy, and continence nursing (WOC), was founded in 1958 at Cleveland Clinic, Cleveland, Ohio. Pioneering colorectal surgeon Rupert B. Turnbull, M.D., joined forces with former patient Norma Gill to improve care and rehabilitate people with ostomies and enterocutaneous fistulae.