Characterization of FAP-1 expression and function in thyroid follicular cells.
Human thyrocytes are resistant to Fas-mediated programmed cell death (PCD). It has been reported that a labile protein inhibitor is involved in the protection of thyrocytes from PCD, and its action can be reversed by incubation of thyrocytes with cycloheximide (CHX) during treatment with agonist anti-Fas Ab. Fas-associated phosphatase-1 (FAP-1) is a protein that has been shown to interact with the negative regulatory domain of Fas and block Fas-mediated apoptosis in FAP-1 transfected Jurkat cells. We investigated the possibility that FAP-1 might be involved in protection against Fas-mediated PCD in human thyrocytes. FAP-1 mRNA was detected in primary thyrocytes using a ribonuclease protection assay. The presence of FAP-1 protein was confirmed by immunohistochemical staining and flow cytometry using a polyclonal anti-FAP-1 Ab. FAP-1 protein also disappeared from thyroid cells in response to CHX. To determine whether FAP-1 is a functional inhibitor of PCD in thyrocytes, we incubated thyrocytes with synthetic SLV (Ac-SLV) tripeptide to compete with Fas for interaction with FAP-1. Thyrocytes treated with Ac-SLV tripeptide showed significantly increased cell death as compared to cells treated with control tripeptide. In addition, in the presence of a suboptimal concentration of CHX, the Ac-SLV tripeptide yielded a strong, synergistic increase in Fas-mediated PCD as compared to thyrocytes treated with control tripeptide. These results implicate FAP-1 as a regulator of Fas-induced PCD in thyrocytes.
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Department of Internal Medicine, Center for Biologic Nanotechnology, University of Michigan, Ann Arbor 48109, USA.
Arscott
P L
PL
Bretz
J D
JD
Thompson
N W
NW
Baker
J R
JR
D017209:Apoptosis; D002352:Carrier Proteins / Q000235:genetics* / Q000502:physiology*; D003513:Cycloheximide / Q000494:pharmacology; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D054645:Protein Phosphatase 1; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D017027:Protein Tyrosine Phosphatases / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D013961:Thyroid Gland / Q000737:chemistry / Q000378:metabolism*; D019014:fas Receptor / Q000502:physiology
D002352:Carrier Proteins; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D019014:fas Receptor; D003513:Cycloheximide; D054645:Protein Phosphatase 1; C516742:PTPN13 protein, human; D054595:Protein Tyrosine Phosphatase, Non-Receptor Type 13; D017027:Protein Tyrosine Phosphatases