IDENTIFICATION OF PROTEINS THAT ARE ABNORMALLY REGULATED IN DIFFERENTIATED CULTURED HUMAN KERATINOCYTES

Comparison of the protein expression patterns of proliferating normal primary human keratinocytes plated in serum-free medium (SFKM), supple mented with epidermal growth factor (EGF) and bovine pituitary extract (BPE), and similar cultures induced to differentiate by the addition of Dulbecco's modified Eagle medium (DMEM), containing 10% fetal calf serum (FCS), revealed several known and unknown polypeptides that are abnormally regulated in the differentiated cells. Upregulated proteins included keratins (keratins 6, 10/11, 14 and 16), members of the S100 protein family psoriasin, MRP8, MRP14 and S100c), actin-binding prote ins (gelsolin and tropomyosin 9220), annexins (annexins IV and VIII), hsp28, the fatty acid binding protein 5 (FABP5), the squamous cell car cinoma (SCC) antigen, members of the 14-3-3 family, involucrin, E-cadh erin, cystatin A, desmoglein and integrins alpha(2) and beta(1), as we ll as several proteins of as yet unknown identity. The highest upregul ated proteins corresponded to psoriasin (124.0 times), MRP8 (42.4 time s), MRP14 (14.9 times), tropomyosin 9220 (11.5 times), involucrin (11. 1 times), and FABP5 (9.1 times). FABPS, hsp28, and tropomyosin 9220 we re also highly upregulated in quiescent keratinocytes indicating that their increased levels in the differentiated cell may be due to loss o f proliferative activity. Highly downregulated proteins included PAI-2 , tropomyosins 9213, 9121 and 9122, keratin 5, calnexin, 14-3-3 beta a nd eta, nucleoside: diphosphate kinase A, Rho GDIs, hsp60, hnRNPs H an d C2, alpha-enolase, eIF-4D, thioredoxin, annexins III and V, moesin, nucleolar protein B23, GST pi and PCNA/cyclin. Both the high expressio n of keratin 6 and 16 - which are markers for an alternative pathway o f keratinocyte differentiation - as well as the extremely high upregul ation of some members of the S100 protein family indicate that the cel ls have differentiated via an abnormal pathway.