Calpain Isoforms in the Eye

Retina and lens from rodents contain at least five newly discovered isoforms of calpain (Lp82, Lp85, Rt88, Rt88′ and Rt90), in addition to the ubiquitous calpains. Unexpectedly, these isoforms were related to muscle-preferred p94. Although some of their biochemical characteristics are known, the current challenge is to discover the functions of calpain isoforms under normal and pathological conditions. Further, because of stop codons, orthologues of the isoforms discussed above do not exist in man. Another challenge is to relate the rodent data to the human situation. For example, do undiscovered calpain isoforms performing the same functionsas Lp82, Lp85, Rt88 and Rt90 exist in human eye?