Your instinct is to control and protect. You share only what comes back to you in income, stature, security, promotions, or more control and influence.
The company is not selfish. You are.
Your company wants you to succeed, but it needs to grow. And it feeds on the very communication you block and overmanage.
You must find the common ground between your self-interests and other departments/divisions to meet your company's needs. Your company is bigger and more important to you than you realize.
I can't believe I even have to explain this to you, but apparently you're not alone; it's one of the most common problems I've observed. This doesn't mean you should feel better because so many people are guilty of this offense. On the contrary, it means you need to differentiate yourself as someone who understands how much more trusting, insightful, and open you ought to be.
No one is threatening your job. Your company needs and wants you to be in control and in charge of your area. It just wants you to share what others in your organization need from you. The company's left hand needs to know what its right hand is doing; if it doesn't, it will confuse itself, then confuse its customers, then lose money.
Have confidence that this communication will come back to you in even greater returns.
Contact Ken at email@example.com