PROLACTIN IN MAMMALSBy: Megan the epic M, Erica the fried squid pickel, Abby, Alyssa, Katie, Hiba

GLAND• Prolactin is produced in the pituitary gland in

response to pregnancy and nursing.

• Peptide-based• It is a pituitary polypeptide• Alpha helix folded

BASE

PATHWAY/MECHANISM• Peptide hormone binds to a receptor on the outside

of the cell membrane which activates the Jak2 kinase. Stat5, a transcription factor, is activated by Jak2. Stat5 then goes into the nucleus and hooks onto the DNA triggering a cellular response.

PROLACTIN’S CELLULAR RESPONSE

• Differentiation of the mammary gland which causes the production of the milk proteins.

• WAP- encodes for milk proteins• BLG- encodes for milk proteins• Casein- encodes for milk proteins

NEGATIVE FEEDBACK LOOP

• Suckling is the major stimulus of prolactin production

• Thyrotropin-releasing factor stimulated by hypothalamus.

• TRH is sent to pituitary gland • Pituitary gland releases prolactin • Prolactin stimulates milk production

in breasts beginning in late pregnancy and sustained after birth.

• When the mother no longer needs to produce milk, dopamine inhibits prolactin by signaling the hypothalamus to stop.

ALTERING PATHWAY• In malignant tissues prolactin fails to trigger,

differentiation, and instead enhances breast epithelial survival and motility.

• Prolactin, when over-expressed, inhibits apoptosis in cervical cancer cells