Great news ! I have found a solution that’s work perfectly on Mac OS X El Capitan (10.11) !
As I my uploads worked fine on Arduino Pro Mini with my FTDI breakboard and suitable Apple Signed driver , I have tried to use it with Arduino Uno, but it didn’t work …
After long reads in forums and several try, I have finally found the solution that’s work perfectly !
You have to use an FTDI breakboard (Sparkfun) in replacement of built-in Atmega USB chip.
Once you have an FTDI breakboard, download driver :
Step 1: Install Driver
=>Once done, and break board connected to your Mac, you will show “FT232R USB UART” in detailled system information, under USB
Step 2 : Wiring (BB = Breakboard)
BB GND to Arduino GND
BB VCC to Arduino VCC
BB TX0 to Arduino RXD
BB RXI to Arduino TXD
and the last most special wiring => BB DTR to Arduino Reset with 100nF capacitor between DTR pin and Reset pin (In my case, it didn’t work, but with an additional 100nF capacitor to reach 200nF, it works fine !!)
Step 3 : Arduino IDE
Select >Tools > Port: "/dev/cu.usbserialA700e5Q6
Step4 : Upload as usual … and have fun