Popliteal venous aneurysm (PVA) is rare, and the most frequently reported surgical repair is tangential aneurysmectomy and lateral venorrhaphy. A 60 year old man presented with bilateral pulmonary embolism and a left 4.6 × 4.4 × 7.9 cm partially thrombosed saccular PVA with a1 cm neck. Anticoagulation was initiated and a vena cava filter was inserted two weeks prior to surgery.

BACKGROUND:Postoperative readmissions not only burden the healthcare system but may also affect clinical outcomes of cancer patients. Despite this, little is known about readmissions after cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC), or their impact on survival outcomes.PATIENTS AND METHODS:A single-institution retrospective cohort study of CRS-HIPEC procedures from April 2001 and September 2019 was performed. Early readmission (ERA) was defined as hospitalization within 30 days of discharge post-CRS/HIPEC, while late readmission (LRA) was defined as hospitalization between day 31 and 90 after discharge. Patient demographic, oncological, and perioperative factors were analyzed to identify predictors of readmission, and comparison of survival outcomes was performed.RESULTS:Overall, 342 patients who underwent CRS-HIPEC were included in the study. The incidence of ERA and LRA was 18.5% and 7.4%, respectively. High-grade postoperative complication was the only independent predictor of ERA (HR 3.64, 95% CI 1.47-9.02), while comorbid hypertension (HR 2.71, 95% CI 1.17-6.28) and stoma creation (HR 2.83, 95% CI 1.23-6.50) were independent predictors for LRA. Patients with readmission had significantly worse disease-free survival than patients who had no readmission (NRA) (LRA 1.1 years, ERA 1.2 years, NRA 1.8 years, p = 0.002), and patients with LRA had worse median overall survival (2.1 years) than ERA patients (3.3 years) or patients without readmission (4.4 years) (p < 0.001).CONCLUSIONS:Readmission following CRS-HIPEC is associated with adverse survival outcomes. In particular, LRA may portend worse prognosis than ERA.

Cyclic AMP and cyclic GMP are ubiquitous second messengers that regulate the activity of effector proteins in all forms of life. The main effector proteins, the 3',5'-cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) and the 3',5'-cyclic guanosine monophosphate (cGMP)-dependent protein kinase (PKG), are preferentially activated by cAMP and cGMP, respectively. However, the molecular basis of this cyclic nucleotide selectivity is still not fully understood. Analysis of isolated cyclic nucleotide-binding (CNB) domains of PKA regulatory subunit type Iα (RIα) reveals that the C-terminal CNB-B has a higher cAMP affinity and selectivity than the N-terminal CNB-A. Here, we show that introducing cGMP-specific residues using site-directed mutagenesis reduces the selectivity of CNB-B, while the combination of two mutations (G316R/A336T) results in a cGMP-selective binding domain. Furthermore, introducing the corresponding mutations (T192R/A212T) into the PKA RIα CNB-A turns this domain into a highly cGMP-selective domain, underlining the importance of these contacts for achieving cGMP specificity. Binding data with the generic purine nucleotide 3',5'-cyclic inosine monophosphate (cIMP) reveal that introduced arginine residues interact with the position 6 oxygen of the nucleobase. Co-crystal structures of an isolated CNB-B G316R/A336T double mutant with either cAMP or cGMP reveal that the introduced threonine and arginine residues maintain their conserved contacts as seen in PKG I CNB-B. These results improve our understanding of cyclic nucleotide binding and the molecular basis of cyclic nucleotide specificity.

Cyclic guanosine monophosphate (cGMP) and cyclic AMP (cAMP)-dependent protein kinases (PKG and PKA) are closely related homologs, and the cyclic nucleotide specificity of each kinase is crucial for keeping the two signaling pathways segregated, but the molecular mechanism of cyclic nucleotide selectivity is unknown. Here, we report that the PKG Iβ C-terminal cyclic nucleotide binding domain (CNB-B) is highly selective for cGMP binding, and we have solved crystal structures of CNB-B with and without bound cGMP. These structures, combined with a comprehensive mutagenic analysis, allowed us to identify Leu296 and Arg297 as key residues that mediate cGMP selectivity. In addition, by comparing the cGMP bound and unbound structures, we observed large conformational changes in the C-terminal helices in response to cGMP binding, which were stabilized by recruitment of Tyr351 as a "capping residue" for cGMP. The observed rearrangements of the C-terminal helices provide a mechanical insight into release of the catalytic domain and kinase activation.

BackgroundcAMP-dependent protein kinase (PKA) and cGMP-dependent protein kinase (PKG) are the main effectors ofdistinct cyclic nucleotide pathways and are preferentiallyactivated by cAMP or cGMP, respectively.We recently characterized the isolated C-terminal cyc-lic nucleotide binding domain (CNB-B) of the humanPKG Ib as highly cGMP-selective (manuscript in pre-paration). In a crystal structure of the CNB-B two novelcGMP-specific interaction sites were identified in addi-tion to the previously described threonine residue (T317)in the phosphate binding cassette [1]. Mutation of eachindividual site resulted in reduced cGMP-selectivity andinterfered with cGMP-dependent activation of PKG Ib.To gain further insight into the molecular basis of cyc-lic nucleotide selectivity, we inserted two cGMP-specificinteraction sites into the CNB-B of human PKA RIa bymutating corresponding residues. We hypothesize thatthis way cGMP-specific interaction contacts can be cre-ated in PKA and thereby modulate cAMP-selectivity[1,2].ResultsWe characterized a deletion construct of the PKA hRIaCNB-B as cAMP-selective using fluorescence polarization(FP) and surface plasmon resonance (SPR).In comparison to the wildtype PKA hRIa CNB-B, singlemutant constructs showed similar affinities for cAMP-and cGMP-analogs, revealing a loss of selectivity. Thecombination of two mutations led to a construct withhigher affinity for cGMP compared to cAMP.Co-crystal structures of this double mutant with cAMPor cGMP, respectively, showed that the cGMP-specificinteraction contacts retained their function in the contextof the PKA hRIa CNB-B.ConclusionThegeneralstructureofcyclicnucleotidebindingdomains is conserved. However, varying amino acids inthe binding pocket enable the distinction between cAMPand cGMP. Here we show that cGMP interaction sitesfound in PKG do restore their specific binding mechan-isms when introduced into PKA.The results underline the relevance of the describednovel binding sites in mediating cGMP-selectivity. Still,other features of CNB domains involved in the specificbinding mechanism as well as the detailed mechanism ofkinase activation need to be investigated.

Background Cyclic guanosine monophosphate (cGMP) is a key secondary messenger that is produced in response to nitric oxide. One of the key mediators of cGMP signaling, cGMPdependent protein kinase (PKG), is activated upon binding to cGMP and phosphorylates downstream substrates in a process required for important physiological processes such as vasodilation, nociception, and memory formation. PKGs are also known to mediate most effects of drugs that increase cellular cGMP levels, including nitric oxidereleasing agents and phosphodiesterase inhibitors, which are used for the treatment of angina pectoris and erectile dysfunction, respectively. It is known that PKG is preferentially activated by cGMP over cAMP roughly 60-100 fold – however, the molecular mechanism by which cGMP is distinguished from a structurally similar messenger, cAMP, is poorly defined. Using competition fluorescence polarization (FP), X-ray crystallography, and in vitro kinase assays, we sought to understand the molecular basis for cGMP selectivity in PKGI.