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POGLUT2 and POGLUT3 O-glucosylate multiple EGF repeats in fibrillin-1, -2, and LTBP1 and promote secretion of FBN1

ABSTRACT: Fibrillin-1 (FBN1) is the major component of extracellular matrix microfibrils, which are required for proper development of elastic tissues including heart and lung. Through protein-protein interactions with latent TGF-beta binding protein 1 (LTBP1), microfibrils assist regulation of TGF-beta signaling. Mutations within the 47 epidermal growth factor-like (EGF) repeats of FBN1 cause autosomal dominant disorders including Marfan Syndrome that disrupt TGF-beta signaling. We recently identified 2 novel protein O-glucosyltransferases, Protein O-glucosyltransferase 2 (POGLUT2) and Protein O-glucosyltransferase 3 (POGLUT3), that modify a few EGF repeats on Notch. Here, using mass spectral analysis, we show that POGLUT2 and POGLUT3 also modify over half of the EGF repeats on FBN1, fibrillin-2 (FBN2), and LTBP1. While most sites are modified by both enzymes, some sites show a preference for either POGLUT2 or POGLUT3. POGLUT2 and POGLUT3 are homologs of POGLUT1, which stabilizes Notch proteins by addition of O-glucose to Notch EGF repeats. Like POGLUT1, POGLUT2 and 3 can discern a folded versus unfolded EGF repeat, suggesting POGLUT2 and 3 are involved in a protein folding pathway. In vitro secretion assays using recombinant FBN1 revealed reduced FBN1 secretion in POGLUT2 knockout, POGLUT3 knockout, and POGLUT2 and 3 double knockout HEK293T cells compared to wild type. These results illustrate that POGLUT2 and 3 function together to O-glycosylate protein targets, and that these modifications play a role in secretion of target proteins.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Daniel Williamson

LAB HEAD: Robert S. Haltiwanger

PROVIDER: PXD025725 | Pride | 2021-08-06

REPOSITORIES: Pride

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			Action	DRS
	CS011320_1_LTBP1_TV8_P2_KO_run2.raw	Raw
	CS011320_1_LTBP1_TV8_P2_KO_run2.xlsx	Xlsx
	CS011620_1_LTBP1_TV8_P3_KO_run2.raw	Raw
	CS011620_1_LTBP1_TV8_P3_KO_run2.xlsx	Xlsx
	CS011620_2_LTBP1_T_P2_KO_run2.raw	Raw

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POGLUT2 and POGLUT3 O-glucosylate multiple EGF repeats in fibrillin-1, -2, and LTBP1 and promote secretion of FBN1

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