Additive energetic contributions of multiple peptide positions determine the relative promiscuity of viral and human sequences for PDZ domain targets.

Protein-protein interactions that involve recognition of short peptides are critical in cellular processes. Protein-peptide interaction surface areas are relatively small and shallow, and there are often overlapping specificities in families of peptide-binding domains. Therefore, dissecting selectivity determinants can be challenging. PDZ domains are a family of peptide-binding domains located in several intracellular signaling and trafficking pathways. These domains are also directly targeted by pathogens, and a hallmark of many oncogenic viral proteins is a PDZ-binding motif. However, amidst sequences that target PDZ domains, there is a wide spectrum in relative promiscuity. For example, the viral HPV16 E6 oncoprotein recognizes over double the number of PDZ domain-containing proteins as the cystic fibrosis transmembrane conductance regulator (CFTR) in the cell, despite similar PDZ targeting-sequences and identical motif residues. Here, we determine binding affinities for PDZ domains known to bind either HPV16 E6 alone or both CFTR and HPV16 E6, using peptides matching WT and hybrid sequences. We also use energy minimization to model PDZ-peptide complexes and use sequence analyses to investigate this difference. We find that while the majority of single mutations had marginal effects on overall affinity, the additive effect on the free energy of binding accurately describes the selectivity observed. Taken together, our results describe how complex and differing PDZ interactomes can be programmed in the cell.

Additive energetic contributions of multiple peptide positions determine the relative promiscuity of viral and human sequences for PDZ domain targets.

Protein-protein interactions that include recognition of short sequences of amino acids, or peptides, are critical in cellular processes. Protein-peptide interaction surface areas are relatively small and shallow, and there are often overlapping specificities in families of peptide-binding domains. Therefore, dissecting selectivity determinants can be challenging. PDZ domains are an example of a peptide-binding domain located in several intracellular signaling and trafficking pathways, which form interactions critical for the regulation of receptor endocytic trafficking, tight junction formation, organization of supramolecular complexes in neurons, and other biological systems. These domains are also directly targeted by pathogens, and a hallmark of many oncogenic viral proteins is a PDZ-binding motif. However, amidst sequences that target PDZ domains, there is a wide spectrum in relative promiscuity. For example, the viral HPV16 E6 oncoprotein recognizes over double the number of PDZ domain-containing proteins as the cystic fibrosis transmembrane conductance regulator (CFTR) in the cell, despite similar PDZ targeting-sequences and identical motif residues. Here, we determine binding affinities for PDZ domains known to bind either HPV16 E6 alone or both CFTR and HPV16 E6, using peptides matching WT and hybrid sequences. We also use energy minimization to model PDZ-peptide complexes and use sequence analyses to investigate this difference. We find that while the majority of single mutations had a marginal effect on overall affinity, the additive effect on the free energy of binding accurately describes the selectivity observed. Taken together, our results describe how complex and differing PDZ interactomes can be programmed in the cell.

Continuation of Contraception Following Termination of Pregnancy in a Canadian Urban Centre.

OBJECTIVE: Minimal evidence exists on the continuation of contraception following termination of pregnancy. Continuation of effective contraception is important because it has been found to reduce unintended pregnancies. This study aims to determine the rate of continuation and choice of contraception following termination of pregnancy. METHODS: A cross-sectional analytic study was undertaken of 400 patients undergoing termination of pregnancy over 2 years. Demographic information and contraception choice prior to, at time of, and 6 months following termination were collected. Data were analyzed to assess relationships between patient characteristics and contraceptive choice. RESULTS: Prior to termination, 58.5% of patients were not using contraception and 22.4% used a less effective method (e.g., barrier or fertility awareness). Following termination, 99.7% of patients chose a method of contraception, and 95.2% chose a more effective method (e.g., long acting reversible contraception, permanent sterilization, combined hormonal contraceptives, progesterone-only contraceptive). Six months following termination, 85.8% of patients were using contraception. A more effective method was continued by 37.8%. There were no significant relationships between choice of contraception and age, previous pregnancies, or social determinants of health. Patients living with their sexual partner were significantly more likely to switch to a less effective method of contraception at 6 months. CONCLUSIONS: Following termination of pregnancy, almost all patients chose a method of contraception and most continued using contraception 6 months following termination.

Coping with cancer: examining the supports available to women with gynecologic cancer at Saskatoon Cancer Center.

OBJECTIVE: When women are diagnosed and treated for gynecologic cancer, they must find ways to cope. Cancer is both a physically and emotionally challenging disease. This study aims to identify existing coping strategies in women diagnosed with gynecologic cancer throughout their cancer journey and to add to these supports to help women cope with their cancer. METHODS: Women with gynecologic cancer were interviewed individually according to focus group principles during scheduled clinic visits at Saskatoon Cancer Center to identify coping strategies following diagnosis and treatment of cancer. Interviews were used to inform researchers before preparing a survey about coping with cancer. During 8 weeks, women receiving care were surveyed. Questions explored diagnosis, therapy phase, feelings, attitudes, and support. RESULTS: Sixteen women were interviewed; questionnaires were distributed to 75 women with cervical (20.7%), uterine (22.2%), ovarian (60.3%), and vulvar cancer (1.6%). After diagnosis, the major support was family in 96.8%, and talking helped in 71.4%. All women found their gynecologic oncologist and nurse were easy to talk to/supportive. Only 12.7% attended counseling, 17.5% attended workshops/patient education sessions, and 9.5% attended support groups. Reasons for not receiving supportive counseling were voiced. A small number of alternative therapies tried by 60.3% were deemed helpful in 97.4%. Parking at the cancer center was a stressor in 81%. Participants felt that the Saskatoon gynecologic cancer care team fulfilled their needs emotionally. Patients want information about workshops, support meetings, and other modalities to improve their quality of life during their cancer journey. CONCLUSION: Providing better quality and type of available supports may enhance the experience of women following diagnosis and during therapy for cancer and will help women to cope with cancer more effectively.