Coronary heart disease (CHD)2 is one of the prime causes of an increase in the mortality rate worldwide. Over the past few years, various epidemiological studies have provided ample evidence that increased levels of HDL, by transporting cholesterol from atherosclerotic plaques to liver for excretion, can arrest the progression of CHD (1, 2). Subsequent preclinical studies on overexpression of apolipoprotein A-I (apoA-I), the major protein constituent of HDL, have reported significant reduction in CHD risk (3, 4). Although raising HDL levels is a longstanding strategy for mitigating CHD risk, the current lipidtargeted therapies, including the usage of statins, fibrates, and niacin, have shown reduced therapeutic potential (5-7). Hence, there is a continuous requirement for new strategies that can elevate HDL levels to halt the progression of CHD.Cholesteryl ester transfer protein (CETP), a plasma glycoprotein with 476 residues, has been found to mediate the transfer of cholesteryl esters (CEs) from HDL to LDL and VLDL as well as the reciprocal transfer of triglycerides (TGs) from LDL and VLDL to HDL (8, 9). The identification of deficient CETP gene levels and correlated high HDL levels in a Japanese population (10 -13) brought CETP into focus as a therapeutic target for controlling HDL levels. Preclinical animal model studies have further substantiated these findings by showing an elevated level of HDL in mice with non-expressing CETP (14 -16). Since then, the inhibition of CETP activity by small molecule inhibitors has been pursued as an active approach to prevent atherosclerosis with varying levels of success at clinical trial phases (17)(18)(19)(20). Given the complexity of lipid metabolism and the pivotal role of CETP in the process, understanding CETP structure, CETP inhibition, and the mechanism by which CETP transfers neutral lipids is of prime importance. The last decade, therefore, has seen the employment of sophisticated techniques, like cryo-EM (21, 22), x-ray (23, 24), and MD simulations (25-28) on this front. Nevertheless, the story of CETP remains far from complete.The crystal structure of CETP (Protein Data Bank entry 2OBD) has been solved with four bound lipid molecules (23). The structure shows two ␤-barrel domains at the N and C termini, each with a twisted ␤-sheet and a long ␣-helix; a central ␤-sheet between the two ␤-barrels; a C-terminal ␣-helix; and a 60-Å-long hydrophobic tunnel occupied by two CE molecules. Additionally, there were two plug-in dioleoylphosphatidylcholine molecules with polar headgroups exposed to plasma and acyl chains buried in the hydrophobic tunnel of CETP. Interestingly, one of the CEs in the hydrophobic tunnel was in the bent conformation, whereas the second CE molecule was in the linear conformation. Recent cryopositive staining EM and optimized negative-staining electron microscopy (OpNS-EM) protocols combined with CETP C terminus-specific polyclonal antibody studies have suggested that CETP penetrates its C-terminal ␤-barrel domain into LDL or VLDL and its N-termi...

Chimeric antigen receptor (CAR) tonic signaling, defined as spontaneous activation and release of proinflammatory cytokines by CAR-T cells, is considered a negative attribute because it leads to impaired antitumor effects. Here, we report that CAR tonic signaling is caused by the intrinsic instability of the mAb single-chain variable fragment (scFv) to promote self-aggregation and signaling via the CD3ζ chain incorporated into the CAR construct. This phenomenon was detected in a CAR encoding either CD28 or 4-1BB costimulatory endodomains. Instability of the scFv was caused by specific amino acids within the framework regions (FWR) that can be identified by computational modeling. Substitutions of the amino acids causing instability, or humanization of the FWRs, corrected tonic signaling of the CAR, without modifying antigen specificity, and enhanced the antitumor effects of CAR-T cells. Overall, we demonstrated that tonic signaling of CAR-T cells is determined by the molecular instability of the scFv and that computational analyses of the scFv can be implemented to correct the scFv instability in CAR-T cells with either CD28 or 4-1BB costimulation.

Voltage dependent anion channel (VDAC) of mitochondria plays a crucial role in apoptosis. Human VDAC-1, reconstituted in planar lipid bilayer showed reduced conductance when treated with curcumin. Curcumin interacts with residues in the α helical N-terminus of VDAC and in the channel wall, as revealed by molecular docking, followed by mutational analysis. N-terminus mimicking peptide showed conformational changes in circular dichroism, upon curcumin treatment. We propose that the interaction of curcumin with amino acids in N-terminus and in channel wall fixes the α helix in closed conformation. This restricts its movement which is required for the opening of the channel.

2 The abbreviations used are: RyR, ryanodine receptor ion channel; FKBP, FK506-binding protein; ANOVA, analysis of variance; PDB, Protein Data Bank; IP 3 , inositol 1,4,5-trisphosphate.

The small intestine is the major site for nutrient absorption, which is critical in maintenance of euglycemia. Leptin, a key hormone involved in energy homeostasis, directly affects nutrient transport across the intestinal epithelium. Catestatin (CST), a 21-amino acid peptide derived from proprotein chromogranin A, has been shown to modulate leptin signaling. Therefore, we reasoned that leptin and CST could modulate intestinal Na+-glucose transporter 1 (SGLT1) expression in the context of obesity and diabetes. We found that hyperleptinemic db/db mice exhibit increased mucosal mass, associated with an enhanced proliferative response and decreased apoptosis in intestinal crypts, a finding absent in leptin deficient ob/ob mice. Intestinal SGLT1 abundance was significantly decreased in hyperleptinemic, but not leptin-deficient mice, indicating leptin regulation of SGLT1 expression. Phlorizin, a SGLT1/2 inhibitor, was without effect in an oral glucose tolerance test in db/db mice. The alterations in architecture and SGLT1 abundance were not accompanied by changes in the localization of intestinal alkaline phosphatase, indicating intact differentiation. Treatment of db/db mice with CST restored intestinal SGLT1 abundance and intestinal turnover, suggesting a cross-talk between leptin and CST, without affecting plasma leptin levels. Consistent with this hypothesis, we identified structural homology between CST and the AB-loop of leptin and protein-protein docking revealed binding of CST and leptin with the Ig-like binding site III of the leptin receptor. In summary, downregulation of SGLT1 in an obese type 2 diabetic mouse model with hyperleptinemia is presumably mediated via the short form of the leptin receptor and reduces overt hyperglycemia.

Advances in protein design have brought us within reach of developing a nanoscale programming language, in which molecules serve as operands and their conformational states function as logic gates with precise input and output behaviors. Combining these nanoscale computing agents into larger molecules and molecular complexes will allow us to write and execute “code”. Here, in an important step toward this goal, we report an engineered, single protein design that is allosterically regulated to function as a ‘two-input logic OR gate’. Our system is based on chemo- and optogenetic regulation of focal adhesion kinase. In the engineered FAK, all of FAK domain architecture is retained and key intramolecular interactions between the kinase and the FERM domains are externally controlled through a rapamycin-inducible uniRapR module in the kinase domain and a light-inducible LOV2 module in the FERM domain. Orthogonal regulation of protein function was possible using the chemo- and optogenetic switches. We demonstrate that dynamic FAK activation profoundly increased cell multiaxial complexity in the fibrous extracellular matrix microenvironment and decreased cell motility. This work provides proof-of-principle for fine multimodal control of protein function and paves the way for construction of complex nanoscale computing agents.

Cholesteryl ester transfer protein (CETP) facilitates the bidirectional exchange of cholesteryl esters and triglycerides between high-density lipoproteins and low- or very low-density lipoproteins. Recent studies have shown that the impairment of lipid exchange processes of CETP can be an effective strategy for the treatment of cardiovascular diseases (CVDs). Understanding the molecular mechanism of CETP inhibition has, therefore, attracted tremendous attention in recent past. In this study, we explored the detailed mechanism of CETP inhibition by a series of recently reported small molecule inhibitors that are currently under preclinical testing. Our results from molecular dynamics simulations and protein-ligand docking studies suggest that the hydrophobic interactions between the CETP core tunnel residues and inhibitor moieties play a pivotal role, and physical occlusion of the CETP tunnel by these small molecules is the primary mechanism of CETP inhibition. Interestingly, bound inhibitors were found to increase the plasticity of CETP, which was explained by principal component analysis that showed a larger space of sampling of CETP C-domain due to inhibitor binding. The atomic-level details presented here could help accelerate the structure-based drug-discovery processes targeting CETP for CVD therapeutics.

Catestatin (CST), an endogenous anti-hypertensive/anti-adrenergic peptide, is a novel regulator of cardiovascular physiology. Here, we report case-control studies in two geographically/ethnically-distinct Indian populations (n≈4000) that showed association of the naturally-occurring human CST-Gly364Ser variant with increased risk for hypertension (age-adjusted odds ratios: 1.483, p=0.009 and 2.951, p=0.005). Consistently, 364Ser allele carriers displayed elevated systolic (up to ~8 mmHg, p=0.004) and diastolic (up to ~6 mmHg, p=0.001) blood pressure. The variant allele was also found to be in linkage disequilibrium with other functional SNPs in the CHGA promoter and nearby coding region. Functional characterization of the Gly364Ser variant was carried out using cellular/molecular biological experiments (viz. peptide-receptor binding assays, nitric oxide [NO], phospho extracellular regulated kinase [ERK] and phospho endothelial nitric oxide synthase [eNOS] estimations) and computational approaches (molecular dynamics simulations for structural analysis of wild-type [CST-WT] and variant [CST-364Ser] peptides, and docking of peptide/ligand with beta-adrenergic receptors [ADRB1/2]). CST-WT and CST-364Ser peptides differed profoundly in their secondary structures and showed differential interactions with ADRB2; while CST-WT displaced the ligand bound to ADRB2, CST-364Ser failed to do the same. Furthermore, CST-WT significantly inhibited ADRB2-stimulated ERK activation suggesting an antagonistic role on ADRB2 unlike CST-364Ser. Consequently, CST-WT was more potent in NO production in human-umbilical-vein-endothelial-cells as compared to CST-364Ser. This NO producing ability of CST-WT was abrogated by ADRB2 antagonist ICI 118551. In conclusion, CST-364Ser allele enhanced the risk for hypertension in human populations, possibly via diminished endothelial NO production due to altered interactions of CST-364Ser peptide with ADRB2 as compared to CST-WT.