Moody's Investors Services on Tuesday said it was cutting its long-term rating for Plano-based J.C. Penney Co. (NYSE: JCP) a step lower into junk grade status. CNBC reported that Moody's lowered the retailer's corporate family and probability of default ratings to "B3" from "Ba3," with a negative outlook. Moody's downgrade reflected its concerns about J.C. Penney's fourth-quarter profitability. Last week, Fitch Ratings lowered its rating for J.C. Penney by two notches from B to double-B-minus,…