Former Sears Holding Corp. CEO Eddie Lampert, a longtime key stockholder in AutoNation Inc., is again accumulating shares in the retailer after several years of cutting his stake. AutoNation, the country’s largest new-vehicle retailer, disclosed in a form filed May 10 with the Securities and Exchange Commission that Lampert increased his stake in AutoNation to 17.1 percent from 12.9 percent. Through shares held by his ESL Investments Inc. hedge fund and The Lampert Foundation, Lampert maintains his status as AutoNation’s second-largest shareholder. Altogether, the former Sears executive owns 15.2 million AutoNation shares. He previously disclosed ownership of 11.49 million shares. Microsoft founder Bill Gates remains AutoNation’s largest shareholder, even after selling more than a million shares in the dealership group in recent weeks. Gates disclosed in an SEC form on May 6 that he’d sold 1.07 million AutoNation shares in open-market transactions from April 26 through May 6. The Bill and Melinda Gates Foundation Trust owned 1,898,717 AutoNation shares on Dec. 31. It now owns 824,769 shares.