S100A4 downregulates filopodia formation through increased dynamic instability

Cell migration requires the initial formation of cell protrusions, lamellipodia and/or filopodia, the attachment of the leading lamella to extracellular cues and the formation and efficient recycling of focal contacts at the leading edge. The small calcium binding EF-hand protein S100A4 has been shown to promote cell motility but the direct molecular mechanisms responsible remain to be elucidated. In this work, we provide new evidences indicating that elevated levels of S100A4 affect the stability of filopodia and prevent the maturation of focal complexes. Increasing the levels of S100A4 in a rat mammary benign tumor derived cell line results in acquired cellular migration on the wound healing scratch assay. At the cellular levels, we found that high levels of S100A4 induce the formation of many nascent filopodia, but that only a very small and limited number of those can stably adhere and mature, as opposed to control cells, which generate fewer protrusions but are able to maintain these into more mature projections. This observation was paralleled by the fact that S100A4 overexpressing cells were unable to establish stable focal adhesions. Using different truncated forms of the S100A4 proteins that are unable to bind to myosin IIA, our data suggests that this newly identified functions of S100A4 is myosin-dependent, providing new understanding on the regulatory functions of S100A4 on cellular migration.

The efficacy and safety of imeglimin as add-on therapy in patients with type 2 diabetes inadequately controlled with sitagliptin monotherapy

OBJECTIVE: This 12-week study assessed the efficacy and tolerability of imeglimin as add-on therapy to the dipeptidyl peptidase-4 inhibitor sitagliptin in patients with type 2 diabetes inadequately controlled with sitagliptin monotherapy. RESEARCH DESIGN AND METHODS: In a multicenter, randomized, double-blind, placebo-controlled, parallel-group study, imeglimin (1,500 mg b.i.d.) or placebo was added to sitagliptin (100 mg q.d.) over 12weeks in 170 patientswith type 2 diabetes (mean age 56.8 years; BMI 32.2 kg/m2) that was inadequately controlled with sitagliptin alone (A1C ≥7.5%) during a 12-week run-in period. The primary ef ficacy end point was the change in A1C from baseline versus placebo; secondary end points included corresponding changes in fasting plasma glucose (FPG) levels, strati fication by baseline A1C, and percentage of A1C responders. RESULTS: Imeglimin reduced A1C levels (least-squares mean difference) from baseline (8.5%) by 0.60% compared with an increase of 0.12% with placebo (between-group difference 0.72%, P < 0.001). The corresponding changes in FPG were -0.93 mmol/L with imeglimin vs. -0.11 mmol/L with placebo (P = 0.014). With imeglimin, the A1C level decreased by ≥0.5% in 54.3% of subjects vs. 21.6% with placebo (P < 0.001), and 19.8%of subjects receiving imeglimin achieved a decrease in A1C level of ≤7% compared with subjects receiving placebo (1.1%) (P = 0.004). Imeglimin was generally well tolerated, with a safety pro file comparable to placebo and no related treatment-emergent adverse events. CONCLUSIONS: Imeglimin demonstrated incremental efficacy benefits as add-on therapy to sitagliptin, with comparable tolerability to placebo, highlighting the potential for imeglimin to complement other oral antihyperglycemic therapies. © 2014 by the American Diabetes Association.