Parathyroid hormone stimulates protein kinase C but not adenylate cyclase in mouse epidermal keratinocytes

Intact human parathyroid hormone, hPTH [1–84], and the hPTH [1–34] fragment stimulated membrane‐associated protein kinase C (PKC) activity in immortalized (but still differentiation‐competent) murine BALB/MK‐2 skin keratinocytes. Unexpectedly, the hormone and its fragment did not stimulate adenylate cyclase. The failure of PTH to stimulate adenylate cyclase activity was not due to the lack of a functioning receptor‐cyclase coupling mechanism because the cells were stimulated to synthesize cyclic adenosine monophosphate (cyclic AMP) by the β‐adrenergic drug isoproterenol. Thus, skin keratinocytes seem to have an unconventional PTH receptor that is coupled to a PKC‐activating mechanism but not to adenylate cyclase. These observations suggest that normal and neoplastic skin keratinocytes respond to the PTH‐related peptide that they make and secrete.