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. Author manuscript; available in PMC: 2015 May 19.

Published in final edited form as: J Cell Physiol. 2015 Jan;230(1):226–236. doi: 10.1002/jcp.24704

Models of elastic fiber assembly in Ltbp4S^−/− and Fbln5^−/−;Ltbp4S^−/− lungs. A. Normal Lungs. In normal (WT) lungs elastic fiber assembly requires self-assembly of fibrillin molecules into microfibers as well as secretion and micropolymerization of tropoelastin molecules. Elastin polymerization is catalyzed by lysyl oxidase (LOX) or lysyl oxidase like-1 (LOXL-1) enzymes. LOX interacts with fibullin-4, whereas LOXL-1 interacts with fibulin-5. LTBP-4 interacts with both fibrillin and fibulin-5 and promotes elastogenesis. B. Ltbp4S^−/− Lungs. In Ltbp4S^−/− lungs self-assembly of fibrillin is not affected and there is normal formation of microfibers. However, large elastin aggregates form, as there is no carrier protein to target fibulin-5-elastin complexes to or along microfibers. Only a small fraction of elastin is integrated into the microfibers, presumably through the direct interaction of fibulin-4 and fibulin-5 with fibrillin-1. C. Fbln5^−/−;Ltbp4S^−/− and Fbln5^−/− lungs. In Fbln5^−/−;Ltbp4S^−/− as in Fbln5^−/− lungs, the large elastin aggregates do not form, because there is no initial accumulation of fibulin-5-elastin complexes. Elastogenesis occur through an alternative pathway presumably involving the integration of fibulin-4-elastin complexes into microfibrillar scaffolds rather than the integration of LTBP-4-fibulin-5-elastin complexes into microfibers.

Models of elastic fiber assembly in Ltbp4S^−/− and Fbln5^−/−;Ltbp4S^−/− lungs. A. Normal Lungs. In normal (WT) lungs elastic fiber assembly requires self-assembly of fibrillin molecules into microfibers as well as secretion and micropolymerization of tropoelastin molecules. Elastin polymerization is catalyzed by lysyl oxidase (LOX) or lysyl oxidase like-1 (LOXL-1) enzymes. LOX interacts with fibullin-4, whereas LOXL-1 interacts with fibulin-5. LTBP-4 interacts with both fibrillin and fibulin-5 and promotes elastogenesis. B. Ltbp4S^−/− Lungs. In Ltbp4S^−/− lungs self-assembly of fibrillin is not affected and there is normal formation of microfibers. However, large elastin aggregates form, as there is no carrier protein to target fibulin-5-elastin complexes to or along microfibers. Only a small fraction of elastin is integrated into the microfibers, presumably through the direct interaction of fibulin-4 and fibulin-5 with fibrillin-1. C. Fbln5^−/−;Ltbp4S^−/− and Fbln5^−/− lungs. In Fbln5^−/−;Ltbp4S^−/− as in Fbln5^−/− lungs, the large elastin aggregates do not form, because there is no initial accumulation of fibulin-5-elastin complexes. Elastogenesis occur through an alternative pathway presumably involving the integration of fibulin-4-elastin complexes into microfibrillar scaffolds rather than the integration of LTBP-4-fibulin-5-elastin complexes into microfibers.